Value chain · CLM-1307
In plain terms
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.
The claim as recorded
The IEA-PVPS Task 12 net energy guidelines define EROI as the energy delivered to society over a system's life divided by the energy invested in it, with every investment counted as its life cycle primary energy demand, and allow two numerators: electricity as delivered (EROI_el) or its equivalent primary energy (EROI_PE-eq = EROI_el / G, where G is the life cycle energy efficiency of the grid where the system is deployed); stating which one is used is mandatory. The guidelines' worked example, a rooftop multi-crystalline silicon system at 1,700 kWh/m2 a year, 14.1 per cent module efficiency, performance ratio 0.75, 30 years and 2,444 MJ/m2 invested, gives an EROI_el of 7.9 and, at G = 0.32, an EROI_PE-eq of 25, so one system's EROI moves by a factor of about 3 on convention alone.
Evidence behind this: T3: an IEA-PVPS Task 12 methodology guideline with named authors. It recommends; its mandatory reporting items bind only studies that claim to follow it, so this is not the normative-instrument (T1) case, as ruled for its companion SRC-187 on 2026-09-11.
Scope and limits
The guidelines are written for PV; applying them to SBSP is this register's use, not the document's. The page does not say which grid G = 0.32 represents (unverified). SRC-187 cites this report as Raugei et al. 2015 under the title "Methodology Guidelines"; the held document is titled "Methodological Guidelines", numbered T12-07:2016 and dated January 2016 (PDF p.2). The identity rests on matching authors and subject and is unverified for a separate 2015 version. CLM-1038 (DOE 1980) counts electricity inputs at four times their energy, a different convention, so its ratios are not on this basis. The guidelines' 2021 second edition (IEA-PVPS T12-20:2021) has not been read.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
PDF p.12 Eq. 1: EROI = Out / Inv. PDF p.13 point 2: investments to be expressed as their life cycle primary energy demand, i.e. their Cumulative Energy Demand (paraphrase); point 3: converting output to primary energy is to follow a replacement logic based on the current technology mix of the country or region (its grid mix for electricity), with exergy- or price-based conversions discouraged (paraphrase); footnote 2: primary energy on a higher heating value basis; footnote 3: the total mix, renewable plus non-renewable, is recommended for the numerator (paraphrase). PDF p.14: unless numerator and denominator are both in primary energy the net energy difference is not consistently defined, and with the primary energy numerator EROI becomes a relative indicator readable only against the mix assumed replaced (paraphrase). PDF p.16 Eq. 2 and 3, G = 1/CED of the grid, and the worked example values (data credited to de Wild-Scholten 2013). PDF p.17: EROI_PE-eq depends on the grid's efficiency as well as the system's, so a change over time may reflect the grid (paraphrase); "it is considered mandatory to always specify the chosen approach to perform the EROI calculation". Our arithmetic: 1,700 x 3.6 x 30 = 183,600 MJ/m2; x 0.141 = 25,888; x 0.75 = 19,416; / 2,444 = 7.94; / 0.32 = 24.8, which the page rounds to 25.
Basis: dimensionless ratios in MJ/MJ; EROI_PE-eq = EROI_el / G; worked example per m2 over 30 years
Related records
- Answers question
- QST-008 not published in this releaseQST-021 not published in this release
Cite this
energyaperture.com/c/clm-1307
CLM-1307, Energy Aperture, as of 2016-01.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-646
- CLM-0316In 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...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...CLM-1309A fair energy-return comparison of SBSP with ground solar counts the same things for both: the energy to build, run and scrap each...CLM-1310The 2016 guidelines recommend default lifetime, wear-out and performance numbers for a ground solar energy-return study, and list 16 facts...