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| Factor set | Electricity | Mains gas | Used for |
|---|---|---|---|
| SAP 10.2 | 0.136 | 0.210 | Part L 2021 compliance — the version most new homes in England are assessed in today |
| SAP 10.3 | 0.086 | 0.214 | the Future Homes Standard, for new homes notified from 24 March 2027 |
| DESNZ 2026 | 0.13096 (0.14395 with grid losses) | 0.18231 | company carbon reporting (SECR); gas is burning it, on gross calorific value |
kg CO₂e per kWh. The SAP version you need depends on the building: SAP 10.2 for work under Part L 2021, which covers most new homes being assessed in England today, and SAP 10.3 for the Future Homes Standard. For a company carbon footprint or SECR return, use DESNZ's figure — the full set is on our UK carbon conversion factors page.
That electricity is now lower than gas under every set is the whole reason a heat pump beats a boiler — it wasn't true a decade ago, when the grid was far dirtier. The fixed factors aren't the same thing as the live grid intensity, which changes by the hour as wind and solar rise and fall: you can watch it in GridMonkey.
Source: SAP 10.2 and SAP 10.3 (BRE) emission factors; DESNZ, Greenhouse gas reporting: conversion factors 2026 — UK electricity, T&D and natural gas (gross CV). Figures are illustrative UK equivalents.
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Frequently asked questions
Why is the electricity factor lower than gas?
Because the grid has decarbonised fast — much more wind and solar, and coal gone. Every current official set reflects that, which is why electrified heat now carries less carbon than burning gas.
Which factor should I use?
SAP 10.2 (0.136) for a Part L 2021 calculation, SAP 10.3 (0.086) for one under the Future Homes Standard, and DESNZ's 0.131 — plus 0.01299 for transmission losses — for company carbon reporting.
Is the live grid figure different?
Yes — real-time grid intensity varies through the day and is often below the fixed compliance factors. GridMonkey shows it live.