Savings
Carbon saving (UK Government conversion factors 2026)
- where
- annual carbon saving (kgCO₂e)
- annual fuel saved (kWh)
- emission factor (kgCO₂e/kWh)
- lifetime carbon saving (tCO₂e)
- measure lifetime (years)
Explain this equation
Estimates the carbon saved each year and over the life of a measure.
The emission factor is the CO₂ equivalent released per kWh of the fuel saved, from the government's annual conversion factors. Fuel saved times the factor gives kilograms a year; times the lifetime, divided by 1000, gives tonnes.
Emissions equal energy times emission factor.
Sense check: 5,760 kWh of gas at about 0.18 kg/kWh is about 1.05 tonnes a year, about 31 tonnes over 30 years.
Watch out: if the home later switches to a heat pump, the fuel and its factor change, so the long-term figure is only indicative.
Converts a fuel saving into greenhouse gas emissions avoided, per year and over the life of the measure.
Enter your values to see the result.
Good to know
2026 factors (DESNZ, published June 2026): natural gas 0.18231 kgCO2e per kWh (gross CV, as on gas bills); UK grid electricity 0.13096 kgCO2e per kWh generated (down about 26% on 2025). These are direct (scope 1 or 2) factors; well-to-tank and grid losses are extra if you report them.
Common mistake
Applying today’s electricity factor for 30 years. The grid keeps decarbonising, so lifetime savings for electrically heated homes are overstated.
Limits
Constant factor over the lifetime. Check the factor for the fuel actually used (oil, LPG and so on).
Sources
- DESNZ, Greenhouse gas reporting: conversion factors 2026 (published 11 June 2026)
- Keslio, UK Government 2026 conversion factors (2026 flat file: natural gas 0.18231 kgCO2e/kWh gross CV; UK electricity generated 0.13096 kgCO2e/kWh)
- DESNZ, 2026 GHG conversion factors major changes report (UK electricity −26%; no major changes to fuels)
Results are calculations from the published methods and figures shown, and depend on the data you enter. Follow BS EN ISO 6946, BS 5250, PAS 2035, Building Regulations Part L and manufacturers’ data. Whole-house retrofit needs a qualified retrofit assessor and coordinator.