XC02 Economics and finance
Depth of coverage
At its target depth of L3. What the depth levels mean.
What this layer covers
LCOE, capex, opex, learning rates, discount rates, financing, insurance, subsidy, first-unit funding
Where it ends
Cross-cutting: tag alongside the layer whose cost it describes
Deep area
This layer is studied in more depth than most. It belongs to the deep area Economics and levelised cost (LCOE).
What it would cost
Published estimates of what space solar electricity would cost run from a few pence to more than a dollar per kilowatt-hour. No full-scale space solar power station has been built or tested, so no cost estimate has been checked against a real one (CLM-1444). NASA's 2024 study puts its two designs at 0.61 and 1.59 USD/kWh in its baseline case (CLM-0123). Its own sensitivity runs reach 0.03 and 0.08 USD/kWh if several assumptions improve together (CLM-0124). A 2021 UK study puts the fifth unit built at about 5 pence per kWh in its central case, in 2018 prices at a 20 per cent required return (CLM-0170). Restated to 2024 pounds, a 20-year life and a common discount rate, the yearly rate used to reduce future costs to today's value, the UK first-unit estimate and this site's own calculation of NASA's estimate still differ by 19 to 37 times (CLM-0379). Evening out the discount rates widens the gap rather than closing it (CLM-0380). The largest identified cause is the assumed cost of lifting each kilogram to the orbit where the satellite works (CLM-0382).
Records
249 of the 291 records tagged to this layer are published. The rest are not yet published. A record is published only after a second reader has checked it and it has passed every publication check. What the gate checks.
| Record | In plain language | Tier | Confidence |
|---|---|---|---|
| CLM-0018 | The most recent UK government report calls 230 watts per square metre a limit to be reached because it lowers cost, and cites an earlier report by the same consultancy as the reason for using it. | T4 | HIGH |
| CLM-0019 | The report sets out Space Solar's plan: a small in-orbit test, then 31 megawatts in 2030, 150 megawatts in 2033, and 650 megawatts in geostationary orbit in 2036. | T4 | MED |
| CLM-0023 | In the 1978 reference design, two limits set the size of the transmitter and the receiving site: how much heat the transmitter can shed, and an upper limit on beam strength taken from studies of the ionosphere. | T3 | HIGH |
| CLM-0037 | In its unaudited accounts for 2025, the holding company behind the CASSIOPeiA design reported net assets of about 1.3 million pounds and 1.07 million pounds of convertible loans, and said it owed about 859,000 pounds to a related investor. | T1 | HIGH |
| CLM-0042 | The 230 watts per square metre figure applies to one frequency and one design lineage. Japanese designs at a higher frequency allow up to about eight times as much. | T0 | MED |
| CLM-0060 | In 1981 a NASA review panel said the 230 watts per square metre figure rested on an obsolete theory with no experimental support, and made resolving it the top priority. | T3 | HIGH |
| CLM-0063 | NASA suggested in 1981 that 550 to 600 watts per square metre might be reasonable, roughly two and a half times the figure still in use, and said the parameter decides the system size and has billions of dollars of cost impact. | T3 | HIGH |
| CLM-0066 | The figure adopted in 1978 was higher than each of the lower figures in the studies it cited, though those figures were themselves uncertain by up to a factor of two. | T0 | HIGH |
| CLM-0067 | According to a 2007 international report, Japanese designs of the time chose their beam strength on cost and land grounds; the report does not give the ionosphere as the reason. | T2 | HIGH |
| CLM-0087 | The biggest thing deciding this threshold is a human choice about which plasma structure size matters. The choice of radio frequency matters least. The two atmospheric terms are upper bounds, not clean figures, because they were varied independently when they are actually linked. | T0 | HIGH |
| CLM-0118 | Storms big enough to disturb the ionosphere over the UK happen on roughly 12 to 18 days a year on average, mostly around solar maximum. Which figure is right is not yet known. | T3 | LOW |
| CLM-0123 | NASA's own 2024 study puts space solar power at 12 to 80 times the cost it expects in 2050 from power stations on the ground, a set it calls renewable but which includes nuclear, with launch the dominant cost. | T3 | HIGH |
| CLM-0124 | NASA also found that if several things improve at once, rather than just one, space solar power does become cost competitive. | T3 | HIGH |
| CLM-0144 | A NASA study found that launching everything into space is by far the biggest cost of a space solar power system, and that most of those launches would just be carrying fuel to move earlier payloads from a low orbit up to the final, much higher orbit, not carrying useful hardware. | T3 | HIGH |
| CLM-0170 | A UK government-commissioned study estimates the cost of electricity from a mature (fifth-built) space solar power satellite at roughly 3.5 to 7.9 pence per kWh in 2018 money, but this swings by almost 3x depending on how much it costs to launch things into orbit. | T4 | HIGH |
| CLM-0171 | The same model shows the cost of electricity is noticeably higher for the first unit built than for the fifth, and when this study compares its solar-power-satellite cost to wind and solar costs, those comparator figures do not include the cost of storing or backing up wind and solar power, so it is not a fully like-for-like comparison. | T4 | HIGH |
| CLM-0172 | The study uses a high assumed rate of return (20%) to work out the headline cost-per-unit-of-electricity figure, but uses a much lower official government rate (3.5%) when working out whether the whole programme is worth public money - these are not the same number and should not be confused. | T4 | HIGH |
| CLM-0173 | Developing a working space solar power system for the UK is estimated to cost somewhere between about 7.5 and 16 billion pounds (in 2021 prices on the report's own statement for this table) over 18 years, with the higher number reflecting a standard government allowance for cost overruns. | T4 | HIGH |
| CLM-0174 | On the study's own numbers, a first space solar power system would not, by itself, earn investors the return they would expect (20%) - it would need the UK government to fund roughly half, or more than three-quarters once normal cost overruns are allowed for, of the development cost before private money would follow. | T4 | HIGH |
| CLM-0175 | For every pound of public money put into the whole programme, the study estimates the UK economy gets back between GBP 1.30 and GBP 1.80. It counts only the publicly funded share of spending, and values wider economic activity rather than just electricity sold. | T4 | MED |
| CLM-0177 | The cost model assumes the satellite gets cheaper to build the more of them are made, using a range that runs from the faster cost-learning of a 2010s space-industry estimate (Mankins) down to the slower cost-learning the study estimates for SpaceX's Starlink constellation; separately, it assumes the system generates power 100% of the time with zero downtime, which the study's own authors call optimistic. | T4 | HIGH |
| CLM-0178 | The UK government's own summary of this study repeats the same headline figures as the underlying technical report: about 5 pence per kWh, a development cost of around 16 billion pounds, and an estimated 1.80 pounds of wider economic benefit for every pound spent. | T4 | HIGH |
| CLM-0179 | This 2025 paper's own numbers show that with today's technology, their space solar power design would cost about $7.78 per kWh - far more expensive than any terrestrial option - and only becomes competitive (9.4 cents/kWh) if 10 years of assumed technology improvement and cost learning happen first. | T2 | HIGH |
| CLM-0180 | The low headline cost figure in this paper depends on using a very low 2% discount rate borrowed from a US home-energy-efficiency programme, not a rate reflecting the financial risk of building a brand-new kind of space infrastructure - the authors themselves flag that a different, riskier financing situation would need a different (higher) rate. | T2 | HIGH |
| CLM-0188 | A 2012 NASA-funded concept study shows its own cost estimate falling from about $3.26 per kWh for a small near-term system down to about 9 cents per kWh for a much bigger system built with assumed future technology improvements - and the author states plainly that this headline low figure is only an early-stage estimate ("TRL 3"), not a validated cost. | T3 | LOW |
| CLM-0189 | A separate 2022 study for the European Space Agency, by Frazer-Nash and London Economics, estimates the cost of electricity from a first full-scale unit, with investors expecting a 20% return, at between about 11 and 21 euro cents per kWh, and notes that if launch costs could reach levels already being observed for reusable NASA/SpaceX flights (about 400 euros per kg), the technology would become genuinely competitive. | T4 | HIGH |
| CLM-0190 | This European study finds that a full Europe-wide space solar power programme would cost about 418 billion euros in today's money but return about 600 billion euros in benefits once the value of avoided fossil fuel generation, avoided CO2 emissions and R&D spillovers are all counted - a net benefit of roughly 150 to 260 billion euros depending on assumptions, and a net loss of about 171 billion euros if all its costs doubled. The value put on avoided CO2 emissions (about 233 billion euros) is larger than the whole net benefit, so the result rests on that valuation rather than on the electricity itself. | T4 | HIGH |
| CLM-0191 | This 2022 report is one of two parallel studies the European Space Agency commissioned on the costs and benefits of space solar power: this one used the CASSIOPeiA design and was done by Frazer-Nash with London Economics; the report says the other, by Roland Berger and OHB on a different design, was done independently. | T4 | HIGH |
| CLM-0192 | The full list of assumptions behind the headline result of NASA's 2024 study, that space solar power would cost far more than ground alternatives, includes a launch cost of $850-1,000 per kilogram, only a 10-year satellite lifetime, and a solar cell efficiency of 35% - each of these, not just launch cost, is doing some of the work in producing the high headline cost figure. | T3 | HIGH |
| CLM-0193 | To get to a competitive cost, NASA's own 2024 analysis needs launch costs to halve, solar cells to get much more efficient, satellites to last half as long again, and manufacturing to get cheaper faster, all at the same time, not just one improvement on its own; and there is a small but real inconsistency inside the NASA report itself about exactly how low the resulting cost estimate for the smaller design (RD1) is - Table 3 says 4 cents per kWh, the summary text says 3 cents. | T3 | HIGH |
| CLM-0194 | This 2010 paper predicts that if enough solar power satellites were built to justify mass-producing reusable rockets, launch could eventually cost around USD 400-450 per kilogram, against over USD 10,000 per kilogram at the time of writing, and this would add only about 2 US cents per kilowatt-hour to the price of the electricity produced. | T5 | MED |
| CLM-0195 | In 2025 the whole world launched about 2,712 metric tons of satellites into orbit across 325 launches. A single 2010-era plan for solar power satellites assumed that, at its busiest point, over 160,000 metric tons a year and thousands of launches a year would be needed just for that one program. Real-world 2025 launch activity is far below that assumed scale. | T5 | MED |
| CLM-0198 | The same 2010 paper gives two very different price tags, about $650 million and about $5 billion, for storing the same amount of electricity (26 gigawatt-hours, about one day's supply for a city the size of Austin, Texas). The paper does not explain why the two numbers differ. | T5 | HIGH |
| CLM-0199 | The paper estimates that just launching the parts for a 1-gigawatt space solar power satellite would cost at least $25 billion, using 2010-era, pre-reusable-rocket launch prices scaled up from the Ariane V rocket. The author calls this launch cost alone "uneconomic." Adding the cost of building the satellite and the ground antenna brings the total to about $30 billion per gigawatt, which is far above the $1-5 billion per gigawatt the paper cites for building a new fossil-fuel or nuclear power plant. | T5 | HIGH |
| CLM-0240 | A from-scratch cost model of the "Innovative Heliostat Swarm" design gets almost the same electricity cost as NASA's own study: about 62 cents per kWh versus their 61 cents. | T0 | HIGH |
| CLM-0241 | For the "Mature Planar Array" design, an independent cost model built the same way as for the other design gets a materially lower electricity cost than NASA's published figure, even though the underlying costs match closely. | T0 | MED |
| CLM-0242 | Working the power output out from scratch, using only the physics of sunlight and the efficiency losses NASA itself lists, gives the same answer NASA published. | T0 | HIGH |
| CLM-0243 | The huge number of rocket launches NASA calculated for each design can be rebuilt from scratch using just the mass of the hardware, how much a rocket can carry, and how many refuelling trips each delivery needs -- and it comes out almost exactly the same. | T0 | HIGH |
| CLM-0246 | Adding up the costs from scratch -- rockets, factories, spare parts -- gives almost exactly the same total bill NASA calculated, for both designs. | T0 | HIGH |
| CLM-0247 | NASA's published cost figure for the "Mature Planar Array" design may be counting the effect of its low duty cycle twice by mistake, which would make the true figure closer to 1.0 dollars per kWh rather than 1.59. | T0 | MED |
| CLM-0248 | How fast the cost of building each solar-power-satellite module falls as more are made turns out to matter more to the final electricity price than the cost of getting them into orbit -- more than any other single thing tested in this model. | T0 | MED |
| CLM-0249 | Simply choosing a different interest rate to value future costs and income changes the final electricity price about as much as most of the technical improvements NASA tested -- and NASA never actually tested this choice. | T0 | HIGH |
| CLM-0250 | If the design that runs almost all the time had to operate at the same lower duty cycle as the other design, its electricity cost would rise by about two-thirds, all on its own. | T0 | MED |
| CLM-0256 | If several other improvements happen together -- better propulsion, much better solar cells, faster manufacturing learning, and hardware that lasts 15 to 20 years -- then a launch price of roughly 15-30 million dollars per flight would be enough to bring this design's electricity down to about 5 US cents a kilowatt hour. For 2050 NASA projects about 2 to 5 cents for five renewable sources on the ground (wind and solar with storage about 2 cents; geothermal, hydro and solar thermal about 5) and about 5 cents for nuclear, which NASA counts with them though it is not renewable. So 5 cents matches the dearest of these, not the cheapest. | T0 | MED |
| CLM-0257 | For every kilogram of hardware launched into orbit over the station's 30-year life, RD1 generates about 30,000 kilowatt-hours of electricity, and RD2 about 17,500. | T0 | MED |
| CLM-0258 | Every dollar amount in this document is priced as if it were 2022, matching NASA's own report; nothing has been adjusted for inflation to today's prices. | T0 | HIGH |
| CLM-0259 | Building the cost model completely independently still leads to the same overall conclusion NASA reached: today's space-based solar power concepts cost far more than the electricity NASA projects for 2050 from five renewable sources on the ground and from nuclear (about 2 to 5 cents a kilowatt hour), and no single fix closes that gap on its own. | T0 | HIGH |
| CLM-0260 | A U.S. government-linked cost model (formerly NREL, now called the National Laboratory of the Rockies) estimates that plain utility-scale solar power could cost between about 14 and 56 US dollars per megawatt-hour by 2030-2050, depending how fast costs fall and how good the sunlight is at the site. Adding four hours of battery storage to smooth output raises this to about 25-113 dollars per megawatt-hour. These figures do not include the cost of storage large enough to cover a full day or night, so they are not a "24-hour power" cost. | T3 | HIGH |
| CLM-0261 | The same U.S. cost model estimates onshore wind power at roughly 16-73 US dollars per megawatt-hour by 2030-2050, and offshore wind at a much wider 42-460 dollars per megawatt-hour, depending on cost-case assumptions and how good the wind resource is at the site. The high end of the offshore wind range reflects a poor wind site and a pessimistic cost case; it is not a typical or recommended figure. | T3 | HIGH |
| CLM-0263 | A widely used financial-industry cost report estimates 2026 U.S. power costs, without subsidy, as follows: utility solar 40-98 dollars per megawatt-hour, onshore wind 37-99, offshore wind 105-167, new gas power plants 51-129 (combined-cycle) or 144-276 (fast-response peaker plants), new nuclear 175-255, and new coal 72-177. These are today's costs only; the report does not attempt to project what these costs will be in future decades. | T4 | HIGH |
| CLM-0265 | The same report assumes, by default, that a power project is financed 60 percent by debt (at 8 percent interest) and 40 percent by equity investors (who require a 12 percent return), giving a combined after-tax financing cost of about 7.7 percent. It also shows, separately, what happens if that financing cost is higher or lower, from as low as 4.2 percent to as high as 10.0 percent: at the low end, a typical utility solar project costs about 71 dollars per megawatt-hour; at the high end, about 106 dollars. Financing cost matters a lot for a technology like solar or nuclear that is very capital-intensive up front. | T4 | HIGH |
| CLM-0266 | The report itself warns that its main headline cost figures leave out the wider costs of running a reliable power grid, things like power lines, backup capacity, and keeping the system balanced. It also says clearly that it is not trying to predict what power will cost in future years, and that it should not be read as the full cost of supplying electricity to a system, only the cost of building and running one project. This warning matters directly for any comparison against a claim about future, for example 2050, power costs, or against a source that assumes the wider grid costs are already included. | T4 | HIGH |
| CLM-0267 | In 2025, IRENA estimated that new solar power around the world cost about 4.4 US cents per kilowatt hour on average, and onshore wind about 3.3 cents. Other renewables cost more. Each figure is the cost of that technology on its own. | T3 | HIGH |
| CLM-0268 | In 2023, IRENA estimated that new onshore wind farms in Europe cost about 4.6 US cents per unit of electricity on average, and new offshore wind farms in Europe cost about 6.7 cents. For the UK specifically, IRENA gives a slightly lower offshore wind figure of about 5.9 cents per unit. These do not include storage or balancing cost. | T3 | HIGH |
| CLM-0269 | In 2025, IRENA put the cost of building a large battery that can supply power for four hours at about 140 US dollars per kilowatt hour of storage. That is nearly 30 per cent less than a year earlier and about a twentieth of the 2010 cost. | T3 | HIGH |
| CLM-0270 | DESNZ estimated in its 2025 report that a new large solar farm built in the UK and commissioned in 2030 would generate power at about 60 pounds per megawatt-hour (6 pence per kilowatt-hour), and one commissioned in 2050 at about 49 pounds. Onshore wind is estimated at a similar cost; offshore wind is estimated at roughly double the cost of solar or onshore wind. These figures do not include the cost of storing power or balancing the grid. | T3 | HIGH |
| CLM-0271 | DESNZ estimated that a new gas power station in the UK, run almost continuously, would generate power at about 111-112 pounds per megawatt-hour (about 11 pence per kilowatt-hour), whether commissioned in 2030 or 2050. A gas plant with carbon capture, run the same way, is estimated slightly cheaper. These are the closest dispatchable, always-available comparators in this report; they are gas-fired, not firmed renewables. | T3 | HIGH |
| CLM-0272 | The UK government's 2025 cost report does not give a single number for what it would cost to make solar or wind power available around the clock; it says that working this out needs a full power-system model, which this report is not. It also does not publish specific cost figures for the UK's flagship nuclear projects, because those costs are commercially confidential. | T3 | HIGH |
| CLM-0276 | The price the UK government agrees to pay offshore wind farms, per unit of electricity actually generated, dropped sharply from 2015 to 2022, then rose again through 2024 and 2026. In 2023 no offshore wind developer was willing to build at the price on offer, so zero megawatts were awarded that year. These are real, dated contract prices from competitive auctions, not projections, but they are for electricity as generated, not for guaranteed firm delivery. | T3 | HIGH |
| CLM-0277 | The price the UK government agrees to pay solar farms, per unit of electricity actually generated, has stayed close to 46-50 pounds per megawatt-hour (in fixed 2012-price terms) across the last four auction rounds, from 2022 to 2026. This is a real, dated contract price, not a projection, but it is only paid for electricity as generated, with nothing extra for guaranteed delivery. | T3 | HIGH |
| CLM-0278 | The price the UK government agrees to pay onshore wind farms, per unit of electricity actually generated, roughly halved from 2015 to 2022, then rose again through 2024 and 2026. These are real, dated contract prices from competitive auctions, not projections, but they are for electricity as generated, not guaranteed firm delivery. | T3 | HIGH |
| CLM-0279 | A few UK renewable-energy auction contracts are for technologies that can generate more steadily than wind or solar: waste-to-energy plants, biomass-with-heat plants, and a handful of small pilot geothermal plants in Cornwall. Their contracted prices, in fixed 2012-price terms, range from about 46 to 119 pounds per megawatt-hour. These are the best real UK price signals in the register for something closer to firm power, but they are all small in scale and none of them carries a formal obligation to deliver on demand. | T3 | HIGH |
| CLM-0280 | A 2022 ESA-commissioned study modelled that the first European space solar power satellite could produce electricity at a cost of 106 to 206 euros per megawatt-hour. It modelled that this could fall to about 88 to 156 euros per megawatt-hour once ten similar satellites had been built. | T4 | MED |
| CLM-0281 | The study tested how much the cost of launching material into space changes the price of space solar power. It used launch-cost data from about 2022. The report says that if launch costs fell to about 400 euros per kilogram, which it describes as similar to costs seen for reusable SpaceX rockets at the time, space solar power could become highly competitive with other ways of generating electricity. The report does not give a source for the 400 euro figure. | T4 | MED |
| CLM-0282 | A 2022 ESA-commissioned study modelled that, from 2022 to 2070, space solar power for Europe could deliver a net economic benefit of about 183 billion euros, counting avoided costs of building, fuelling and running power plants on the ground, avoided carbon emissions and other benefits. It also modelled that private investors would not fund the first satellite alone unless the government paid for a large share of development: roughly 58 percent if investors need a 20 percent return, or roughly 30 percent if they need a lower 15 percent return. | T4 | MED |
| CLM-0286 | A 2025 peer-reviewed study modelled space solar power inside a detailed model of Europe's future electricity system, using the more favourable of NASA's cost projections for the year 2050, the one that needs several improvements together. It found that one satellite design using mirrors (called RD1) could lower the total cost of Europe's power system by 7 to 15 percent and replace much of the wind and solar power otherwise needed, but only if its projected costs are actually achieved. A second design using flat panels (called RD2) came out too expensive to be worthwhile at its projected 2050 cost. | T2 | MED |
| CLM-0287 | In 2023 and 2024, the UK government awarded about GBP 5.5 million in grants to 9 projects to develop space-based solar power technology and components, through a competition that opened in 2022 and was funded by the UK Space Agency and the old BEIS department. These are awards with named recipients and amounts, not just a plan. The government page lists award values; it does not report how much was paid out. | T3 | HIGH |
| CLM-0296 | A 2025 peer-reviewed study from Caltech modelled its own space solar power design and calculated three costs of electricity: about 778 US cents per kilowatt-hour using today's technology, 9.4 cents after about ten years of development, and 3.8 cents in a long-run best case about twenty years out. The 9.4 cents figure that is often quoted is the middle case, not a present-day cost. The design is small, about 113 megawatts, and converts only about 4 percent of the sunlight it collects into electricity delivered on the ground. | T2 | MED |
| CLM-0297 | The low electricity costs in a 2025 Caltech study rest on two assumptions among others. First, it assumes that SpaceX's Starship will in time launch cargo for about 7 million dollars a flight, falling to 3 million, which works out at roughly 128 dollars and then 55 dollars per kilogram. Those are the authors' own projections, built on the way SpaceX said in 2020 that Starship would reach geostationary orbit and on the long-run fall in launch costs, not prices anyone has paid. Second, it assumes that the money to build the system costs 2 percent a year (a 2 percent discount rate), taken from a US government energy memorandum, which the paper itself says reflects one country's funding arrangements at one moment. With the costs and hardware available when it was published in 2025, the same study's own figure is about 778 US cents per kilowatt-hour. | T2 | MED |
| CLM-0300 | The main international definition of LCOE is the flat price per unit of electricity a power plant would need to be paid, every year of its life, to break even overall. | T3 | HIGH |
| CLM-0301 | The IEA itself says plain LCOE misses how useful a power plant is to the wider electricity system, which is why it built a second, add-on metric. | T3 | HIGH |
| CLM-0302 | The US government's own energy statistics agency warns that comparing plain LCOE across different kinds of power plant, without also looking at value, can be misleading. | T3 | HIGH |
| CLM-0303 | A major financial advisory firm's own widely-used LCOE report says plainly that its numbers do not cover intermittency or total system cost. | T4 | HIGH |
| CLM-0304 | The interest rate assumed changes an LCOE figure a lot, and most for plants that cost the most to build: in a 2020 international study, going from 0% to 20% raised gas plant costs by about 40%, wind and solar by about three times, and nuclear by more than five times. | T3 | HIGH |
| CLM-0305 | How long a power plant is assumed to last matters much less to its cost per unit of electricity than the interest rate does. | T3 | HIGH |
| CLM-0307 | The US government's avoided-cost metric shows that, for the power plants it expects to be built, value and cost are within about 25 percent of each other; for some plants it does not expect to be built, such as offshore wind, coal and nuclear, value is half of cost or less. | T3 | HIGH |
| CLM-0308 | The IEA's alternative metric adds credit for how much a power plant helps keep the grid reliable, on top of its raw energy cost, but the IEA itself says the answer depends heavily on what the future electricity system is assumed to look like. | T3 | MED |
| CLM-0309 | One influential academic paper shows that once you add in the extra cost a variable power source creates for the rest of the grid, its true cost to the system can end up roughly double its own sticker price at high market share. | T2 | HIGH |
| CLM-0310 | How much a solar farm can be relied on to replace a conventional power plant, measured properly, drops sharply as more solar is added to the same grid. | T2 | HIGH |
| CLM-0311 | As more wind or solar power is added to a grid, each additional unit of it earns a lower price on average, because it increasingly arrives when everyone else is also generating. | T2 | HIGH |
| CLM-0312 | A major financial advisory firm has estimated, using US grid operators' own published figures, what it adds to the cost of wind or solar to count them as dependable capacity alongside gas power stations; on its figures the addition is between about 8% and 85% of the plant's own cost, not many times more. | T4 | HIGH |
| CLM-0315 | Even though NASA's own figures say space solar power's carbon footprint is about as good as five renewable sources of power on the ground (NASA also counts nuclear with them, though nuclear is not renewable), that similarity means paying extra for space solar power buys almost no additional carbon saving compared with those low-carbon sources - and even compared with gas, the implied price per tonne of carbon saved is extremely high, about 1,250 to 1,400 dollars. | T0 | MED |
| CLM-0316 | In 2009 three researchers guessed that, once the energy to deliver and use it is counted, an oil-based fuel must return at least about 3 times the energy put into it, and a society's main fuels about 5 times, to support modern life; a search found no open, peer-reviewed calculation of where space solar power sits against such thresholds. | T3 | MED |
| CLM-0317 | Two studies of how much land US ground-mounted solar farms need, the second drawing most of its measurements from the first, indicate once converted to the same units that the receiving antenna of a space solar power design already in the register would need roughly a quarter to a fifth as much ground per unit of electricity delivered. | T0 | HIGH |
| CLM-0318 | Looking across every different way economists and grid operators actually measure how much extra a reliable power source is worth, it is worth a bit more: up to about four times as much when measured as an average across a grid's solar farms, which stays well short of the 12-to-80-times difference space solar power's own cost study found. Measured as the value of the last solar farm added to a grid already full of solar, it can be much larger, and the study behind that figure gives no upper limit. | T0 | MED |
| CLM-0319 | The register's recommended way to check space solar power's economics against something other than plain cost-per-unit is the IEA's value-adjusted cost, whose formula is now public, checked against a US value-for-money ratio whose underlying figures are published, plus a comparison against an illustrative cost of firm, reliable power in today's electricity markets. | T0 | MED |
| CLM-0370 | Converting the UK government's 2021 space solar power cost estimate onto the same money-year, same investment-return and same asset-life basis as the other studies in this comparison gives about 21 to 49 pounds per megawatt-hour, depending on which return rate is used. | T0 | MED |
| CLM-0372 | The second 2022 European Space Agency study cannot be fully converted onto the same basis as the others, because it does not say what investment-return rate or satellite lifespan it assumed for the two cost figures used here. Only the currency and inflation adjustment could be done. | T0 | LOW |
| CLM-0373 | Rebuilding NASA's 2024 space solar power cost estimate from the ground up, then converting it onto the same basis as the other studies, gives roughly 560 to 1,790 pounds per megawatt-hour depending on which design and which return rate is used -- an order of magnitude above the UK and European studies on the same basis (CLM-0389). | T0 | MED |
| CLM-0374 | NASA's own best-case space solar power scenario, if several separate improvements all happen together, converts to roughly 33 to 154 pounds per megawatt-hour on the same basis as the other studies -- broadly similar to the UK and European baseline studies' figures, not to NASA's own baseline figures. | T0 | LOW |
| CLM-0375 | Converting Caltech's 2025 space solar power cost estimates onto the same basis as the other studies gives a huge range on its own: from over 2,600 pounds per megawatt-hour using only today's technology, down to about 23 pounds in the paper's most hopeful case, which it describes as what new design and manufacturing advances might make possible in 20 years. | T0 | LOW |
| CLM-0377 | Before using a shortcut method to work out how much changing the assumed investment-return rate and satellite lifespan would move each study's cost figure, this calculation checked the shortcut against two real answers it could look up. It matched closely (within about 4%) for a small change, but was off by 10 to 30% for a bigger change, which means the shortcut method is good enough to show the direction and rough size of an effect, but not precise enough to trust its last few percent. | T0 | MED |
| CLM-0378 | If every number in this exercise is compared at once, including each study's own best-case and worst-case scenarios, the spread looks even wider than before -- over a hundred times. That is not evidence of new disagreement between institutions; it happens because comparing one study's optimistic best case against another's pessimistic worst case will always look wide, on any subject. | T0 | MED |
| CLM-0379 | Once the UK, European and US flagship studies are all put on exactly the same money-year, investment-return and satellite-lifespan basis, comparing like designs to like designs, the gap between the cheapest and most expensive is still about 19 to 37 times -- essentially unchanged from, and in one comparison larger than, the roughly 20 times found before any of this restatement work was done. | T0 | MED |
| CLM-0380 | Changing the assumed investment-return rate moves any single study's cost estimate a lot on its own, about four to five times. But the cheapest study in this comparison already uses the harshest rate, and the most expensive study already uses the gentlest one. So making the rates the same does not bring the studies together -- it makes clear that something other than the rate is doing the real work of making one study's numbers so much lower than the other's. | T0 | MED |
| CLM-0381 | Two separate UK and European studies of the same satellite design agree that building five to ten of them, instead of just one, cuts the cost of electricity by roughly a fifth to a quarter. That is a real and consistent finding, but it is far too small an effect to explain why different institutions' cost estimates differ by many times over. | T0 | MED |
| CLM-0382 | How much it will cost to get one kilogram of hardware into the right orbit is the single biggest unresolved disagreement in this whole comparison. NASA's assumption is actually higher than the UK and European studies' assumptions, even though NASA uses a far gentler investment-return rate that should have let it show a lower cost, not a higher one -- this is the specific mechanism behind why the studies do not agree even after every other adjustment. Separately, a 2025 US paper's more optimistic scenarios assume launch prices about ninety to two hundred times lower than NASA's, based on a 2020 company planning document rather than any price actually paid. | T0 | MED |
| CLM-0384 | This exercise could not fully convert every study onto the same basis. One study (Roland Berger/OHB) is missing too many basic facts -- what return rate, what satellite lifespan, what launch cost it assumed -- to be rescaled at all beyond a basic currency conversion. Another (Caltech) required a best-guess stand-in for satellite lifespan. And the exchange rates and inflation figures used throughout are remembered rather than freshly looked up, because internet access was not available for this task. | T0 | HIGH |
| CLM-0385 | In order of how much they actually matter: what launch is assumed to cost matters most by far; the choice of investment-return rate matters a lot in isolation but works in the wrong direction to explain why the studies disagree; genuine differences in satellite design matter but cannot be measured precisely from what is available; the size of the satellite probably matters somewhat; building several units instead of one matters a little; and using different currencies and price-years barely matters at all. | T0 | MED |
| CLM-0386 | Even after making the money-year, currency, investment-return rate and satellite lifespan identical across the UK, European and US flagship studies, the gap between the cheapest and most expensive stays at roughly twenty to thirty-five times. Most of the apparent disagreement between these institutions is real, not an artefact of how the numbers were prepared, and the single biggest identified reason is that they assume very different prices for getting hardware into orbit. | T0 | MED |
| CLM-0387 | Caltech's design is a different, much smaller thing from the UK, European and US flagship studies, so its numbers are kept separate rather than folded into the main size-twenty-to-thirty-five comparison. Its own three cost estimates are still useful, but mainly to show how much assumed future technology and launch-price improvement can move one paper's own numbers, not to compare directly against the bigger designs. | T0 | MED |
| CLM-0388 | This is the full list of places where this calculation had to approximate, guess, or simply could not go further, collected in one place so nobody has to hunt through six other records to find them. | T0 | HIGH |
| CLM-0389 | The question was how much of the apparent twenty-times disagreement between major space solar power cost studies was real, and how much was just different currencies, price-years, investment-return assumptions and satellite lifespans. The answer is that almost none of it was bookkeeping. Once everything is put on the same footing, NASA's figures, as rebuilt here, are still 19 to 37 times the UK government-commissioned study's, and less far apart from the European study's, and the single biggest reason is that they assume very different prices for getting a kilogram of hardware into orbit. This is a genuine, unresolved disagreement about a real-world cost, not an artefact of how the numbers were reported. | T0 | MED |
| CLM-0390 | Putting all the cost estimates on the same footing does not make them agree. The disagreement is real, not an accounting artefact. | T0 | MED |
| CLM-0401 | A 2004 review calculated that, under some of the most extreme conditions measured during a large solar storm in October 2003, only just over four fifths of a microwave power beam would get through the ionosphere and atmosphere to the ground, against more than 99.7 per cent normally. The storm lasted more than a day, but conditions varied, so a loss that large probably (our inference) did not last throughout. The standard 1978 efficiency figures include no allowance for it. | T3 | MED |
| CLM-0407 | Cutting the price of a rocket launch brings the electricity cost down to roughly the same low point NASA itself found, using an independently built model. | T0 | HIGH |
| CLM-0408 | If the hardware lasted the full 30-year mission without needing to be replaced twice, the electricity cost would fall by almost half, on its own. | T0 | HIGH |
| CLM-0410 | Switching from chemical rockets that need refuelling to electric thrusters that do not would cut the electricity cost by about two-thirds, matching what NASA itself found. | T0 | MED |
| CLM-0450 | An economic model from about 2011 of a small, first-of-a-kind demonstration solar power satellite found its electricity would cost over 23 USD per kilowatt-hour if privately financed, against roughly 1 USD per kilowatt-hour that the source uses for comparison (generator power at US forward military bases, where its own estimates run from about 0.9 to 27 USD); only full government funding of both development and hardware brought the price down to 0.15 USD per kilowatt-hour, which the authors say may then be competitive on optimistic ground-system costs, in a case they judge unlikely. | T5 | MED |
| CLM-0462 | A 2025 study by the OECD Nuclear Energy Agency and the US Electric Power Research Institute estimates that new large nuclear plants built now would cost about 95 to 168 US dollars per megawatt hour. If the industry gets back to building reactors routinely, that could fall to about 56 to 87 dollars. Extending the life of existing plants is cheapest, at about 39 to 62 dollars. | T3 | HIGH |
| CLM-0465 | Converting the 2022 European Space Agency space solar power cost estimate onto the same basis gives roughly 27 to 110 pounds per megawatt-hour depending on percentile, unit count and return rate used. | T0 | MED |
| CLM-0466 | NASA's report prints the computer code for its cost-learning formula, and running that code gives back the report's own module and servicer costs. The one-line formula written in words just above the code is mistyped, so anyone working from the words rather than the code would get a badly wrong answer. | T0 | MED |
| CLM-0467 | Using much more efficient solar cells would let the whole station be built with far less mass and far fewer launches, and that combined effect cuts the electricity cost by more than a launch-price cut alone would. | T0 | MED |
| CLM-0468 | In this model, free launch alone, with every other input unchanged, still leaves the electricity cost at about 0.10 dollars per kWh or more, because building and replacing the hardware itself costs too much. | T0 | HIGH |
| CLM-0469 | The same U.S. cost model puts new nuclear power at roughly 49-137 US dollars per megawatt-hour and geothermal power at roughly 41-149 dollars per megawatt-hour by 2030-2050, depending on the cost-case assumed. Both technologies can run almost continuously (90 percent of the time or more), so, unlike solar and wind, these figures are already close to a "firm power" cost without needing extra storage. The same source gives building and running costs for new gas power plants and coal plants, but does not publish a matching cost-per-unit-of-electricity figure for them in this edition. | T3 | HIGH |
| CLM-0470 | The same financial-industry report separately estimates what it costs to make solar and wind power as reliable as an always-on power plant, using the rules each U.S. grid operator actually applies to plan for enough capacity at peak demand. Across six major U.S. grid regions, firmed solar (without its own storage) costs about 92-135 dollars per megawatt-hour; solar with four hours of battery storage, also firmed, costs about 115-167 dollars per megawatt-hour. Firmed onshore wind costs about 87-118 dollars, and wind with storage about 103-146 dollars. The report itself is careful to say this "firming cost" is not the same as the cost of building a resource that can run for a full 24 hours a day on one site; it reflects each region's own accepted method of crediting how much a plant contributes to keeping the lights on at peak times. | T4 | HIGH |
| CLM-0515 | Nearly half of the grant money the UK government announced in 2023 and 2024 for its space-based solar power innovation competition was awarded to three projects named after the CASSIOPeiA design; none of the other six awards was tied to a named satellite design. | T3 | HIGH |
| CLM-0517 | Every date in the plan -- the ground demo (2026), the demo mission (2027-28), 2030, 2033 and 2036 -- is a hope, not a booking, and the report that states them says so itself. | T4 | HIGH |
| CLM-0519 | The UK government has not announced any money for the next stage of this design since its 2022-2024 competition, and its own webpage, last updated in February 2026, promises none. | T0 | MED |
| CLM-0522 | The UK study used a 20% return requirement, based on what institutional investors are expected to want. The US study used 3%, on a one-line assumption of government funding, and did not test what a different rate would do. | T4 | HIGH |
| CLM-0523 | Changing the assumed investment-return rate moves a cost estimate a lot on its own, but the cheap study already uses the tough rate and the expensive study already uses the gentle one, so making the rates match does not bring them together. | T0 | MED |
| CLM-0524 | Every UK-specific or typical-country cost-of-capital figure found sits well below the 20% rate Frazer-Nash used, even at the top of DESNZ's published range for floating offshore wind; only a global dataset covering the riskiest countries in the world reaches as high as 20%, and only at its extreme end. | T4 | HIGH |
| CLM-0525 | If a gentler, arguably fairer investment-return rate is used instead of Frazer-Nash's tough 20%, its own cost figure gets even lower, not higher -- but this does nothing to close the huge gap with the US study, because the gap does not come from the discount rate. | T0 | MED |
| CLM-0527 | The tough interest rate Frazer-Nash used for CASSIOPeiA makes its low headline cost figure more impressive, not less, when checked against real-world comparable rates -- but that says nothing about whether the other numbers feeding into that figure are right. | T0 | MED |
| CLM-0528 | NASA's assumptions imply a high cost per kilogram delivered to the power station's actual orbit, mainly because NASA assumes every launch carrying hardware needs twelve extra fuel-only launches to refuel it for the climb from low orbit. | T0 | HIGH |
| CLM-0531 | Neither the UK nor the US figure for what it costs to get a kilogram of hardware into the power station's real orbit is based on an actual, completed transaction. Both are assumptions about future launches, and NASA says it makes no claim that its assumed launch price is reliable. For the same rocket and the same starting price per launch, the two figures differ mainly in how hardware is assumed to get from low orbit to its final orbit, and that is what changes the number of launches needed. | T4 | MED |
| CLM-0532 | A different space-solar-power company's own 2024 analysis estimates that a single non-reused Starship launch to low orbit would cost about $665 per kilogram, and that costs could fall toward $500/kg within a decade. | T4 | MED |
| CLM-0534 | SpaceX's published Falcon 9 price is lower per launch than the 100 million dollars both the US and UK studies assumed, but higher per kilogram, because Falcon 9 carries far less than the rocket those studies assumed. A real government order in late 2025 for five missions averaged more than 100 million dollars each. Neither figure allows for getting from low orbit up to the power station's real orbit. | T6 | MED |
| CLM-0538 | The US and UK studies are not just using different toughness levels for the same test -- they are answering different questions. The US study asks "what would this cost the government to build and pay for entirely by itself," which is why its rate is so low. The UK study asks "what return would a private investor need to put money in," which is why its rate is so high. Whether the same would hold for a real UK project like the new nuclear power station has not been checked against a held source. | T4 | MED |
| CLM-0543 | The US national energy laboratory's 2025 projections have the cost of a four-hour grid battery falling by 2050 in every case it models, to roughly 100 to 300 dollars per kilowatt-hour of storage depending on how fast costs fall. | T4 | MED |
| CLM-0544 | The UK government's own cost model expects deep geothermal power, which it treats as an early-stage technology, to become much cheaper by 2050 than a first-of-a-kind plant would be in 2030. | T3 | MED |
| CLM-0546 | No source in the register, and none found in a general web search, gives a rigorous estimate of what firmed solar or wind power will cost in the 2040s or 2050s. The two pieces that exist (a firming-cost estimate for 2026, and a future battery-cost trend) have not been joined in any source found. | T0 | MED |
| CLM-0547 | Building about 1.46 to 2 million identical satellite modules means the production line has to double its total output about 20 to 21 times over, starting from the first one built. | T0 | HIGH |
| CLM-0559 | None of these five problems, on its own, proves space solar power is impossible for the UK. But solving all of them at once, on the timeline proponents state, would require several separate hard problems to go well together, and right now nobody has the evidence to say confidently that any of them will. | T0 | MED |
| CLM-0600 | NASA's launch price was optimistic, not pessimistic. The expensive part is its assumption that each payload needs twelve refuelling flights, which multiplies the cost thirteen times. | T0 | HIGH |
| CLM-0601 | In one model, swapping refuelling flights for electric-propulsion tugs cuts the electricity cost by about two thirds. NASA's own analysis reports 62 per cent total cost savings for its electric-propulsion variant, and a critic said that using tugs with electric propulsion would be a far more efficient approach. The three are not fully independent, because the model uses NASA's own inputs. | T0 | MED |
| CLM-0683 | If NASA's own numbers for switching to electric propulsion are applied to the existing side-by-side comparison of the big institutional cost studies, the gap between the cheapest and most expensive study shrinks from about twenty-to-thirty-five times down to about seven-to-ten times. That is a large improvement, but the studies still do not agree. | T0 | MED |
| CLM-0689 | The Chinese team published its own cost figures for a one-gigawatt system: about 17.3 billion US dollars over 30 years, which they put at about 6.6 US cents per kilowatt-hour. They say this is more than 30 per cent cheaper than their previous design. | T2 | HIGH |
| CLM-0696 | NASA's own comparison table shows exactly why its headline "0.02 to 0.05 dollars per kilowatt-hour" figure needs care. The cheapest entries in that table are wind and solar without storage, which are not firmed: they generate only when the wind blows or the sun shines. The solar panel entry with storage barely changes how much of the time it can generate, only 30 percent instead of 29 percent, so it is not a round-the-clock supply either. The two entries that genuinely can run almost all the time, nuclear and geothermal, are priced at the top of the range, not the bottom, and so are solar-thermal power with heat storage and hydro. | T3 | HIGH |
| CLM-0697 | The Chinese 6.6 cent figure ignores the cost of money. Once you charge interest on the capital, the same numbers give about 10 cents at a low interest rate and 21 cents at a high one. Even so, NASA's own figures stay between about 2 and 16 times more expensive, depending which of NASA's cases you pick. | T0 | MED |
| CLM-0698 | The Chinese cost table states a transport price of 1,000 dollars per kilogram in its column heading, but its own numbers only work out at about 482 dollars per kilogram. Every row shows the same mismatch, so it is not a rounding error. Either way the figure is far below NASA's assumed 11,050 dollars per kilogram - between 11 and 23 times below, depending which of the two you use. | T0 | MED |
| CLM-0710 | The second European study, which had never been obtained here, is now in the archive. It puts the cost of a two-gigawatt first system at 213 euros per megawatt-hour, leaving out research and decommissioning costs, which is about five times the cost of solar power today and ten times its projected cost in 2050. | T4 | MED |
| CLM-0765 | Searching all fourteen security and defence sources for anything about insurance or liability turns up no premium, no cover limit and no liability figure for any satellite; the only real mention is one reference to the 1972 space liability treaty. | T0 | MED |
| CLM-0786 | In December 2025 the UK system operator changed its own connection standard to allow a single large direct-current converter to carry more power, because the old 1320 megawatt cap was forcing offshore wind farms to build extra cables, and it priced the extra frequency support at about 12 million pounds a year. | T3 | HIGH |
| CLM-0797 | In December 2025 Britain's system operator said that 283 gigawatts of generation and storage, out of more than 700 gigawatts that had been waiting to connect, would be prioritised for connection, split between projects needed by 2030 and by 2035. | T6 | LOW |
| CLM-0814 | A 2020 conference paper's own cost model put the whole 60-satellite programme of the 1978 US reference design at about 3.86 trillion US dollars in present-value terms for either version, and the cost of launching each kilogram of hardware at about 407 dollars for the silicon version and 375 for the gallium-arsenide version. The paper never says which year's dollars these are, although it gives its cost per kilowatt-hour for the same system in 2015 dollars. | T5 | MED |
| CLM-0817 | The authors state openly that a space-solar-power advocacy non-profit paid for this study, that part of the reason was to test or support the environmental marketing claims made for the technology and potentially justify funding future missions, and that the lead researcher says the work was kept rigorous regardless; two of the four authors work for that funder. | T5 | HIGH |
| CLM-0877 | A US regulator's order repeats a spaceflight news site's count of more than 3,500 Starlink satellites launched by October 2022. If that count is right, doubling from one unit to 3,500 takes nearly twelve doublings, and the company must have built at least as many as it launched, so that is a floor rather than an estimate - but the number is a journalist's, carried by the regulator rather than established by it. | T5 | MED |
| CLM-0878 | By late 2022 the Starlink production line had roughly halved the distance to the scale a solar power satellite programme would need, about nine more doublings of output still to go. A doubling means building twice as many as every one built before, so nine of them is a very long way. | T5 | MED |
| CLM-0922 | In 2001 a National Research Council committee found that the basic trade study for the solar array had never been done, and that the mass and cost of getting the array to orbit dominates whatever the array itself costs. Their summary is that making the array free would not fix it. | T3 | HIGH |
| CLM-0932 | A 2010 paper making the case for a national space solar power programme never works out a cost per unit of electricity, and its main system cost comes from an unpublished manuscript; one endnote does a rough fleet cost and return-on-investment sum. It also says the ionospheric and safety concerns look answered at a basic level, without giving a number. | T4 | HIGH |
| CLM-0933 | In 1988 the leading experimenter listed three numbers side by side: the best efficiency physics allows for beaming power and converting it back, 76 per cent; an experimental figure, 54; and what a solar power satellite design assumes, 58 to 72. The design range is above the experimental figure, and its top end is close to the limit. | T3 | MED |
| CLM-0934 | In 1988 the NASA centre running the work said the solar power satellite programme did not stop because the technology failed. It stopped because the up-front investment was more than American utilities would risk, and because the energy crisis ended. The same document reports that the centre's own three-year rectenna research at very high frequencies produced encouraging results and no working devices. | T3 | HIGH |
| CLM-0935 | The IPCC's chapter on energy systems mentions space-based solar power once, in a single sentence, among a list of alternative solar technologies that includes solar chimneys. It says the concept takes advantage of continuous sunlight but faces a formidable obstacle: getting the power down safely, efficiently and cheaply. It gives it no cost, no potential figure, no table row and no section of its own. | T3 | HIGH |
| CLM-0962 | The 1978 US government reference design assumed two satellites would be finished every year for thirty years. That was a starting assumption for the cost work, not something the study worked out. | T3 | HIGH |
| CLM-0967 | The 2022 European study assumed it takes two years to build a satellite in orbit, and that getting parts launched could be the thing that makes it take longer. | T4 | MED |
| CLM-0973 | Apply that same measured pace to the whole satellite rather than just its framework, and the 1978 design would have needed several thousand people, not a few hundred, to finish in six months. The design assumed something made people two to fourteen times more productive and never said what. | T0 | MED |
| CLM-0982 | The famous six months to build a satellite in orbit was decided first and the designs were fitted to it. One contractor says outright that it slowed its machines and cut its crew to make the number come out. | T3 | HIGH |
| CLM-1017 | By 1981 the programme itself said the ionospheric limit it had designed to was probably too cautious, and worked out what relaxing it to more than double would be worth: nearly twice the power from a slightly larger antenna, at a third of the cost penalty. | T3 | HIGH |
| CLM-1022 | A loss you can make up by adding solar panels costs about 56 million dollars per percentage point; a loss at the ionospheric ceiling costs eleven times that, because there is no more beam to give. That is why the ionospheric limit matters economically, and it is the first price on the timing-error budget. | T3 | HIGH |
| CLM-1025 | In 1980 the people building the case set themselves a goal of thirty dollars a kilogram to low orbit, hoped for fifteen later, and said in the same breath that the programme's schedule could not be met. | T3 | HIGH |
| CLM-1028 | Building the rockets was priced at seventeen billion 1977 dollars and running them at about 2.8 billion per satellite, or roughly sixty 1979 dollars for every kilogram of satellite delivered to its final orbit. Most of that was the launcher; the electric ferry was a fifth. | T3 | HIGH |
| CLM-1029 | In 1980 the programme's own accounting had rockets at roughly one dollar in four of a satellite's cost and nearly one in two of the money needed to develop the system, and it noted that the whole programme through the first satellite cost about what NASA had spent from its founding through Apollo. | T3 | HIGH |
| CLM-1030 | The independent 1980 cost review said the government's rocket numbers were fair for the stage the programme was at, then added spare vehicles because the plan assumed nothing would ever fail, roughly doubled the risk on the electric ferry because its unit price assumed a factory that did not exist, struck out the dedicated crew launcher, and put the running cost about eleven per cent higher with a much wider error band. | T3 | HIGH |
| CLM-1035 | In 1981 NASA priced a satellite at 11.5 billion 1977 dollars and the road to the first one at 102 billion, said it was not an official figure, and built the transport line on a launch price that works out at about 24 of those dollars per kilogram to orbit. | T3 | HIGH |
| CLM-1036 | The programme's own sizing arithmetic, with its rate of return stated: in the cases studied a bigger antenna always raised the cost, but much less if the ionospheric limit rose with it. The 152.3 in its cost formula is the capital-recovery factor for 15 per cent over thirty years. | T3 | HIGH |
| CLM-1037 | By the end of 1980 the programme office was saying in writing that its own design limit was too cautious, that fifty or sixty might be reasonable, and that the cost case depended on raising it. | T3 | HIGH |
| CLM-1038 | In 1980 the Department of Energy calculated that a silicon space solar satellite would take six years to pay back the energy that built it, four times longer than coal or nuclear, and that almost all of that was the energy cost of making the silicon cells; with gallium arsenide cells it was a little over a year. | T3 | HIGH |
| CLM-1051 | The DOE studies compared space solar against six power-station types picked by stated rules; ground-based solar cells were put in specifically to be the like-for-like comparison, and fusion because DOE was spending heavily on it, not because it would be ready. | T3 | HIGH |
| CLM-1052 | In 1980 the programme's own numbers had a receiving site of about 200 square kilometres per satellite once a safety margin was included, roughly the same land per unit of energy as ground solar of the day and far more than a coal or nuclear plant, but with no mines or waste sites behind it; and the authors said not to add the columns up. | T3 | HIGH |
| CLM-1057 | The safety study's own picture of the system: about $13 billion of hardware per satellite in 1978 money, 640 people in orbit for six months to build each one, forty heavy launches per gigawatt, a launch site loud at six kilometres and windows rattling at 125, and one rocket failure that could kill a thousand. | T3 | HIGH |
| CLM-1059 | By spring 1980 the engineers, the reviewing panel and the ionosphere experimenters were all saying the beam-intensity ceiling the whole design hung on was too cautious; the table that priced relaxing it was published then, and reprinted unchanged in the 1981 summary. | T3 | HIGH |
| CLM-1060 | The 1980 review did not agree with itself on how much of a satellite's cost was rockets: one paper said over a third, the programme's own table said a quarter of each satellite but nearly half of the money to get to the first one, and one paper's launch rate was double everyone else's. | T3 | HIGH |
| CLM-1061 | In one 1980 volume the satellite cost anywhere from about 2,300 to 3,800 dollars a kilowatt depending on who added what - and the programme office said in print that none of it was official. The high-side cases, as printed, ran to four or five times the base, and one of those printed values may be a total carried into the wrong row. | T3 | HIGH |
| CLM-1062 | In 1980 the launch vehicle that everything was costed on was said by its own designers to be arbitrarily big, and they proposed a rocket a third the size that would save five billion dollars up front for a three per cent higher running cost. | T3 | HIGH |
| CLM-1071 | Running the programme at full stretch was reckoned to employ about half a million people on the ground, nearly all of them in factories, with roughly a thousand in orbit at any moment. | T3 | HIGH |
| CLM-1077 | The ground station was seven million panels holding thirteen billion little antennas, costed at about two and a half billion dollars, about 1.7 million tonnes of steel and nearly seven million cubic yards of concrete, and built by three thousand people in two years. | T3 | HIGH |
| CLM-1078 | Put on stilts in fifty metres of North Atlantic the 1980 rectenna cost fourteen times its land price; strung from cables without its ground screen it came down to about twice, and Europe had a dozen shallow patches of sea to put one in. | T3 | MED |
| CLM-1079 | The one outside firm asked to audit the 1980 cost estimates found the ground-station civil works priced at a third to a fifth of what construction experience said, the solar cells three to thirty times too cheap, and the slip rings ten to twenty times, and said the whole thing assumed breakthroughs it could not count on. | T3 | HIGH |
| CLM-1080 | On the utilities' usual accounting the 1980 satellite could not beat coal or nuclear; on Boeing's whole-life accounting, which counted forty years of fuel, it cost less than half as much; and the economists said either way it would soak up a tenth to a quarter of the country's growth capital. | T3 | HIGH |
| CLM-1081 | The people who would have to buy the power said in 1980 that a five-gigawatt block that could vanish within minutes in the spring and autumn eclipse periods might need six gigawatts of standby, that the ground station would lose two hundred thousand diodes a year, and that American utilities were unlikely to own one until there were some ten. | T3 | HIGH |
| CLM-1082 | Two-fifths of the lower forty-eight states were nominally open to ground stations and sixty of them could be placed near the cities they served; the gallium for one satellite was sixteen times the world's yearly output; and the ground-station dipoles would come off the line at six hundred a second. | T3 | HIGH |
| CLM-1110 | The best near-infrared laser-to-electricity receiver so far turns 56 per cent of the light into electricity, but only when the light is 271 kilowatts per square metre, a thousand times brighter than the microwave design beam. At the level the authors call eye-safe, about 270 times lower, it turns about 30 per cent into a couple of milliwatts, while also carrying gigabit data. | T1 | HIGH |
| CLM-1111 | Before this paper, the best near-infrared laser receivers reached about half efficiency, and only under very bright light; at gentler light they manage a fifth to a bit under a half. Receivers for shorter-wavelength light do better, nearly 69 per cent, but the paper prefers the near-infrared band on eye-safety and atmospheric grounds. | T2 | MED |
| CLM-1113 | This paper does not describe a laser power satellite, though two NASA-funded designs for one exist from 1978-80. It does show how a laser receiver behaves: it needs light about a thousand times brighter than the microwave beam to work well, and even at the level the authors call eye-safe it is about a third as efficient as the microwave receiver. | T0 | MED |
| CLM-1172 | A 2025 UK government study tried two places for the receiving station, Aberdeen and southern England near London. Southern England came out better, because the grid there can take the power almost all the time while Aberdeen's connections would lose a quarter of it. | T4 | MED |
| CLM-1173 | A 1980 European survey for offshore receiving stations looked only at the North Sea and the Channel, left the Atlantic and Mediterranean for later, and listed distance to the grid among its siting factors, though it chose the areas on its offshore factors alone. Because the beam's footprint stretches north to south at those latitudes, coasts running east to west fitted badly. | T3 | MED |
| CLM-1194 | The company's first planned project is sized at 200 MW to the grid from a 732-tonne satellite, running nine-tenths of the time over a 20-year life; a later project is 40 times bigger. | T4 | MED |
| CLM-1212 | A space solar start-up says it has signed a 20-year deal to sell power from orbit to a data-centre company: 100 MW at first, perhaps 250 MW later, received in Illinois. Only the two companies have said so, and no price or start date is given. | T6 | MED |
| CLM-1214 | The company says its beam will be on 99.9 per cent of the time, and that a 2 million dollar development agreement with a US government energy agency (ARPA-E) supports its work. It plans a public power-beaming demonstration in March 2027 and says it expects record efficiency. None of this is independently confirmed. | T6 | LOW |
| CLM-1216 | The company says more customers are lined up. It names none and gives no numbers. | T6 | LOW |
| CLM-1221 | IRENA now prices solar power with batteries built to a 95% reliability level, which its summary does not define. At the best sites, it puts this below 8.5 US cents per kilowatt hour in 2025, down from over 10 cents in 2020. | T3 | MED |
| CLM-1224 | A UK space solar start-up said in 2024 that it had a deal to supply an Icelandic utility with 30 MW from orbit by 2030. | T6 | MED |
| CLM-1225 | A US start-up said in late 2025 that it had beamed power from a plane to the ground, and planned an orbital test in 2028 and its first megawatt from space in 2030. | T6 | MED |
| CLM-1226 | In April 2026 Meta said it had reserved up to 1 GW of future space solar power from Overview Energy, with a test in 2028 and power possibly from 2030. | T6 | MED |
| CLM-1231 | In 2009 a California utility agreed to buy 200 MW from a space solar company by 2016. No held source records what became of it. | T5 | MED |
| CLM-1241 | TerraSpark's boss argues that space solar power cannot be paid for as one giant project. It should be built in small steps that each prove one thing, so that risky early money can give way, step by step, to the cheaper money that pays for power stations. The article gives no figures. | T6 | MED |
| CLM-1243 | The company says it is lining up partners in Japan, the US, Saudi Arabia and Canada, and working with the European Space Agency. It pitches beamed power as something Britain could offer its allies, including for defence and polar sites. It says the ground receivers would be cheap enough to finance even in poorer countries. None of this is backed by named deals or figures in the post. | T6 | MED |
| CLM-1247 | Japan's 2023 national space plan lists space solar power research, led by its science and industry ministries, and aims at eventual practical use without giving a date, size or budget. | T3 | HIGH |
| CLM-1261 | In 2009 California's largest utility signed a deal to buy up to 200 megawatts of power from a space solar company for 15 years, starting in June 2016, from a receiving station in central California. It agreed to pay more than the usual benchmark price, and the details were kept confidential. | T3 | HIGH |
| CLM-1263 | In 2003 ESA planned a two-year set of paper studies to help its member countries decide whether space solar power was worth pursuing. The plan aimed to compare it fairly with solar power on the ground and to pick a few demonstration missions to study, not to fund hardware. | T3 | HIGH |
| CLM-1264 | The plan had three steps. First, check whether space solar makes sense against ground solar, what the law allows, and whether it could power Mars missions. Second, compare system designs and pick up to three. Third, study two or three small demonstration missions in enough detail for ESA to decide whether to go ahead. | T3 | HIGH |
| CLM-1265 | ESA planned to finish the whole set of studies in under two years, roughly 2003 to 2005, with the three steps taking about six, six and eight months. | T3 | HIGH |
| CLM-1268 | In 2003 ESA's own rough internal sums suggested space solar and comparable ground solar would cost about the same, to within a factor of ten, and that a space solar plant would return more energy than it took to build. ESA treated both as unproven and planned studies to check them. | T3 | MED |
| CLM-1269 | When the UK's space solar coalition launched in March 2022, its co-chair told a newspaper that a British system could supply about a third of the country's future electricity by the mid-2040s. He said the effort was looking for 75 million pounds over two years at first, and 300 million pounds over five. | T5 | MED |
| CLM-1275 | A small Canadian group founded in 2025 campaigns for space solar power. It wants tax breaks for companies working on it, a promise that the government will buy the power, and a law it has drafted itself. | T5 | MED |
| CLM-1276 | In 2021 Caltech said a private donor and his wife had given it more than 100 million US dollars since 2013 to set up its space solar power project. The donors would not make money from it. The first test in space was planned for early 2023. | T5 | MED |
| CLM-1280 | In July 2023 Europe's space agency asked researchers for ideas on the safety questions around beaming power from space: effects on people, wildlife, the atmosphere, aircraft and the carbon cost of launches. Ideas were due within four weeks, and the best would compete for jointly funded research projects. | T6 | HIGH |
| CLM-1307 | An "energy return" figure for solar power can be stated in two ways, counting the electricity itself or counting the fuel a power station would have burned to make it, and in the worked example of the 2016 international guidelines the second is about three times larger. Any SBSP figure set beside a ground solar figure has to use the same way of counting. | T3 | HIGH |
| CLM-1308 | "Energy payback time" and "energy return" are two views of one calculation and can be converted only when the lifetime and counting method are known. Neither says how much of the sun's or the fuel's energy a system uses up; that is a separate measure. | T3 | HIGH |
| CLM-1309 | A fair energy-return comparison of SBSP with ground solar counts the same things for both: the energy to build, run and scrap each, including the supply chain, measured at the same point, power into the grid. Storage and round-the-clock supply are not credited to any one technology under these 2016 rules for solar power. | T3 | HIGH |
| CLM-1310 | The 2016 guidelines recommend default lifetime, wear-out and performance numbers for a ground solar energy-return study, and list 16 facts every study must report. An SBSP figure can be checked against the same list to see whether it is comparable. | T3 | HIGH |
| CLM-1380 | NOAA's storm levels G1 to G5 correspond to the Kp disturbance index reaching 5, 6, 7, 8 and 9. | T3 | HIGH |
| CLM-1381 | NOAA's own table confirms the storm-day counts the register was using: about 130 strong, 60 severe and 4 extreme storm days in an average 11-year cycle. | T3 | MED |
| CLM-1382 | At its 2025 year end the UK company Cassiopeia Solar owed slightly more than it owned. Its main asset was about 251,000 pounds of patent costs, and it had four staff on average. | T1 | HIGH |
| CLM-1383 | Almost all of what Cassiopeia Solar owes is owed to other companies in its own group, which the accounts do not name. | T1 | HIGH |
| CLM-1384 | The company has spent about 295,000 pounds on patents, which it writes down over 20 years, and added about 15,000 pounds in the last year. | T1 | HIGH |
| CLM-1389 | Getting a kilogram into orbit has become more than 20 times cheaper since 1960, and the study finds the cost falls by about a fifth every time the total mass ever launched doubles. | T2 | MED |
| CLM-1390 | The study expects launch to keep getting cheaper, to about a tenth of today's average by 2040, but says market power and space debris could slow that. | T2 | MED |
| CLM-1398 | A 2022 survey of real US power plants found that, per unit of electricity, nuclear uses the least land and, of these six, wind farms use the most if the land between turbines is counted; if only the turbine pads and roads are counted, wind uses little land. | T2 | HIGH |
| CLM-1414 | The international nuclear agency's 2025 cost report counts the price paid for carbon emissions as part of what a kilowatt-hour costs, alongside building, running, fuelling and dismantling the plant. | T3 | HIGH |
| CLM-1415 | The 2025 international cost report adds 50 US dollars for every tonne of carbon dioxide a fossil plant emits, the same everywhere, when it works out each plant's cost of electricity. | T3 | HIGH |
| CLM-1416 | A 2022 study for the European Space Agency put the cheapest case for space solar power at about 55 euros per megawatt-hour after adjusting for the value of its electricity, under optimistic costs, a 10% cost of capital and a 30-year life. | T4 | MED |
| CLM-1419 | The Royal Society worked out that a British power system running only on wind and sun, with stored hydrogen to cover calm and dark spells, could supply electricity in 2050 at an average of 52 to 92 pounds per megawatt-hour in 2021 money. Most of that cost is the wind and solar power itself. | T3 | MED |
| CLM-1420 | In the Royal Society's model, only about 15 per cent of Britain's electricity in 2050 comes out of storage, so the price of storage moves the average cost little. Each unit that does come out of storage costs many times more than wind or solar power used straight away. | T3 | MED |
| CLM-1421 | A 2016 Imperial College study run jointly with three renewable-energy companies found that adding wind to Britain's grid in 2030 would bring extra system costs of about 5 to 9 pounds for each megawatt-hour the wind farms produce, compared with adding nuclear, if the grid has a fair amount of storage and other flexibility. Most of that extra cost is back-up power stations for windless periods. | T4 | MED |
| CLM-1422 | Imperial College found that the extra system cost of wind and solar in Britain in 2030 depends heavily on how flexible the grid is: about 40 to 48 pounds per megawatt-hour of their output with no new storage or demand response, but about 5 to 17 pounds once those are added. The figures are measured against nuclear power, not counted from zero. | T4 | MED |
| CLM-1423 | The UK's climate advisers said in 2019 that fitting large amounts of wind and solar power into the grid adds roughly 10 to 25 pounds to each megawatt-hour they produce, when wind and solar supply up to about half to two-thirds of the year's electricity. They also said there is little UK evidence for shares above about a third. | T3 | MED |
| CLM-1424 | The UK's climate advisers broke the extra cost of wind and solar into parts: backup power for peak demand, wasted output and keeping spare plant running, and new power lines. They warned that the parts overlap, so they cannot simply be added up. | T3 | MED |
| CLM-1425 | The UK's climate advisers estimated that a nearly carbon-free power system in 2050 would cost about 4 billion pounds a year more than one built on gas, and that the cost of coping with changeable wind and sun is under a tenth of the total. | T3 | MED |
| CLM-1426 | The UK government estimated in 2020 that a wind or solar farm opening in 2030 brings wider grid costs, compared with a nuclear plant, of between about minus 5 and 17 pounds per megawatt-hour of its output, plus up to 13 pounds for transmission lines, depending on the farm type and on how the rest of the system is built. The figure grows for offshore wind built later. | T3 | MED |
| CLM-1427 | The UK government says its 2020 figures for the wider grid cost of each type of power station show how one small extra plant would change costs, compared with a nuclear plant. They are not the total cost of running a whole power system, and they change with the rest of the system. | T3 | MED |
| CLM-1428 | Britain's grid operator estimated that the cheaper of its two plans for a clean power grid in 2030 would cost about 126 pounds for each megawatt-hour used, in 2024 money, a little more than a plan that misses the climate targets, though NESO calls the costs of all the options similar within the bounds of uncertainty. It counts the capital cost of new plant and grid built since 2023, plus running, fuel and carbon costs, but not the capital cost of plant already built. | T3 | MED |
| CLM-1429 | A search on 13 October 2026 found no published model of Britain's power system that is free to decide how much space solar power to build. One British government study valued small space solar plants in a model by scaling down a much larger assumed plant; the only free-choice model found covers the whole of Europe. | T0 | MED |
| CLM-1430 | Put in 2024 money, a reliable British grid built on wind, sun and stored hydrogen would cost about 61 to 107 pounds per megawatt-hour in 2050. Set against the top of that range, the UK government's space solar study comes in at about half, and NASA's study, rebuilt in 2024 money, at nearly nine times. The two sides are costed differently, so this is a rough guide, not a like-for-like price comparison. | T0 | MED |
| CLM-1431 | In the first week of November 2024 the wind was light: wind made a tenth of Britain's electricity supply, against almost 30 per cent over the year, and gas made half. | T0 | HIGH |
| CLM-1435 | In NASA's design, rebuilt in 2024 money, cutting the launch price to a tenth while keeping everything else the same lowers the cost from about 930 to about 340 pounds per megawatt-hour. That is still about three times the top of the Royal Society's modelled 2050 cost range (about 61 to 107 pounds per megawatt-hour) for a British grid built on wind, sun and stored hydrogen. The UK government's study, for a mature fifth-built satellite, gives about 25 and 67 pounds per megawatt-hour for its low and high launch costs. The two sides are costed differently, so this is a rough guide, not a like-for-like price comparison. | T0 | MED |
| CLM-1444 | The 2021 study for the UK government concluded that space-based solar power is technically feasible, affordable at a competitive cost per unit of electricity, and good for the UK economy, and recommended a staged programme of development and demonstration. This is the study's own conclusion; no such system has been built or tested at scale. | T4 | MED |
| CLM-1445 | The 2021 study for the UK government reports that supporters of space solar power say it has become workable and affordable in the last ten years, after long being seen as attractive but too expensive. The study lists five reasons for the renewed interest: the push to Net Zero, launch costs that have fallen sharply and are expected to keep falling, modular designs built for mass production, maturing solar cells, wireless power and space robots, and other countries' strategic interest. It gives no figures for these on that page. | T4 | MED |
| CLM-1446 | The 1977-80 US government programme did not decide for or against power satellites. It said questions on technology, environment and cost were still open, that a satellite would cost more to build, and less predictably, than conventional power stations, but that the range of its electricity costs was similar to that of other new options of the time, fusion and solar cells. A separate 1981 review for the US Congress said too little was known to decide, that the basic technologies had been shown to be feasible except lasers, and that, except perhaps for fusion, the up-front cost would be much higher than for other large power stations. | T3 | MED |
| CLM-1448 | In 1979, the planners of a space solar power programme expected launch to low orbit to cost about 140 dollars a kilogram in today's money, on a large rocket they planned to fly hundreds of times. A 2026 study puts the average cost over all launches in 2025 at about 3,900 dollars a kilogram in today's money, about 28 times as much. The two numbers are different kinds of figure: one is a forecast for one planned rocket, the other an average over every rocket that flew that year. | T0 | MED |
| CLM-1449 | Britain's solar panels make far less power in winter. In December 2024 they made about a ninth as much as in June. On the worst day of 2024, in late November, they made less than a seventieth of what they made on the best day, in early June. Even within December, the worst day gave about an eighth of the best. | T0 | HIGH |
| CLM-1450 | SpaceX's price sheet lists a Falcon 9 launch at 74 million dollars, and 22,000 kilograms as the most it can carry to low orbit if the rocket is not recovered. Using those listed figures with the US study's own way of counting the extra launches needed to reach the power station's orbit gives a cost per kilogram about four times what the US study's own assumptions give, and the UK study's lowest input would need launches about ninety times cheaper than that listed figure. Both studies turn to electric propulsion for part of the climb, NASA only in the case where it finds a competitive cost, and this has not been shown at power-station scale. | T6 | LOW |
| CLM-1453 | A 2021 UK study estimated what it would cost to carry satellites to high orbit on two reusable launchers: 3,260 dollars a kilogram for SpaceX Starship and 1,340 pounds a kilogram for the British SABRE spaceplane. The study does not set the two side by side in one currency, but converted at any of the exchange rates it lists, the Starship figure is the higher. The cost range its model actually uses runs from 358 to 2,410 pounds a kilogram. | T4 | MED |
| CLM-1457 | A 2021 study for the UK government of the CASSIOPeiA space solar design used two discount rates for two questions: a tough 20 percent, the return it assumed private investors would want, for its cost of electricity, and the government's standard rate at the time, 3.5 percent, for judging whether the whole programme would be worth it for the country. It does not show that pairing the two is standard for other power stations. | T4 | MED |
| CLM-1469 | In the Royal Society's model of a British power system run on wind and sun in 2050, electricity fed into the grid costs about 1.7 to 2 times what the wind and solar power itself costs. At the cheap end, the electricity costs about 1.7 times what the wind and solar power itself costs. At the expensive end it costs about twice as much. | T3 | MED |
| CLM-1476 | The European study states that it used a 3 per cent interest rate for the cost of the space solar satellites. It does not say, in the paper itself, what rate it used for wind, solar and the other power sources, so it is not possible to tell from the paper whether space solar was given an easier test than its rivals. | T2 | MED |
| CLM-1477 | The UK government's 2021 cost study for a power satellite assumes that parts fail and wear over the satellite's life, costing it between nothing and a quarter of a per cent of its output each year. | T4 | MED |
| CLM-1488 | A Royal Society report on storing electricity in Britain, drawing on the Met Office, says a spell of very low winter wind lasting up to a week comes every few years, and a calm summer spell of up to four weeks once every ten years. But in its model of a 2050 grid run on wind and sun, the biggest drain on the store came in the weather of 2009 to 2011, a run of low-wind years. The report warns that studies of single years, or of only the worst spells, can badly underestimate how much storage is needed. | T3 | MED |