Carbon
CO₂e saving from solar generation (UK grid factor)
- where
- annual CO₂e saving (kg/yr)
- annual generation (kWh/yr)
- UK grid emission factor (kgCO₂e/kWh)
- CO₂e saving over the period (t)
- number of years
Explain this equation
Estimates the carbon saved by solar generation, treating each kWh generated as a kWh not taken from the grid.
The grid emission factor is the average carbon released per kWh of grid electricity, published each year by the government. Multiplying the generation by it gives the kilograms saved each year. Multiplying by the years and dividing by 1000 gives tonnes.
Saving equals energy displaced times emission factor.
Sense check: 3,500 kWh at about 0.13 kg/kWh saves about 460 kg a year.
Watch out: the grid factor keeps falling, so savings over many years will be smaller than this year's figure times the years.
An estimate of the greenhouse gas emissions avoided by PV generation, using the UK government grid electricity conversion factor.
Enter your values to see the result.
Good to know
The DESNZ 2026 factor for UK electricity generated is 0.13096 kgCO2e/kWh (2025 data). Adding transmission and distribution losses (0.01299) gives 0.14396 for electricity consumed at the meter, which some argue suits self-consumed generation. Factors fall each year as the grid decarbonises, so a fixed factor over many years overstates the lifetime saving.
Common mistake
Using an old factor (0.2 or more from earlier years), which overstates the saving now that the grid is much cleaner.
Limits
Average (location-based) grid factor, not the marginal plant displaced at the time of generation. Ignores embodied emissions of the system.
Sources
Results are calculations from the published methods and figures shown, and depend on the data you enter. Follow MCS standards, manufacturer data, BS 7671, the ENA connection rules and Building Regulations. System design and DNO applications need a competent, certified installer.