Update, June 2026 factors

The 2026 conversion factors: what changed

Every June, the Government publishes a new set of conversion factors for working out carbon footprints. The 2026 set, published on 11 June, includes the biggest fall in the electricity factor for years. Here is what changed and what it means for your figures.

By Richard Harvie · Updated November 2026 · 5 minute read

In short

The factor for UK electricity fell by 26% and the factor for electricity lost in the grid by 30%. Fuels such as gas, diesel and petrol barely changed.
If you used exactly the same electricity as last year, your Scope 2 emissions would fall by about a quarter without anyone doing anything.
Do not claim that fall as progress. Report your energy use in kWh and litres beside your emissions, so readers can see what really changed.

The main changes

The Department for Energy Security and Net Zero (DESNZ) publishes the factors each year with a report on the main changes. These are the ones most organisations will notice.

Factor	Change from 2025	Why
UK electricity (Scope 2)	Down 26%	Mostly a cleaner grid in 2023 and 2024; a new method also uses data one year old rather than two
Electricity lost in transmission and distribution (Scope 3)	Down 30%	The same new method and more recent grid data
National rail	Down 13%	Passenger numbers and trains updated, replacing estimates based on pre-COVID figures
Light rail and tram	Down 26%	The cleaner grid and updated passenger numbers
London Underground	Down 44% to 45%	The same reasons
International rail	Up about 155%	Services and the use of trains have changed a lot since the pre-COVID figures
Homeworking	Down 31%	Mainly the electricity factor, and the first update since 2022
Electric and plug-in hybrid cars	Most down by around a quarter	The cleaner grid, plus changes in vehicle efficiency
Gas, diesel, petrol, water and waste	No major changes

What it means for your footprint

Take an organisation that uses 1,150,000 kWh of electricity a year, as the worked example in the book does. With the 2026 factor, that comes to about 151 tonnes of CO2e. The same electricity would have been about 204 tonnes with the 2025 factor. That is a fall of around 50 tonnes, without anyone switching anything off.

It is tempting to let that pass as progress. Resist it. Factors can move the other way too, and whoever claimed the fall will then have to explain the rise. It is like your car's fuel gauge being recalibrated: the needle moves, but there is no more fuel in the tank.

How to report it honestly

Use the set that matches your data. For a calendar year, use that year's set. For an April to March year, DESNZ suggests the set for the calendar year in which most of your data falls, so the 2026 set for April 2026 to March 2027. You can also blend two years' factors by the number of days in each. Whichever you choose, say so and stick to it.
Report energy beside carbon. Show your energy use in kWh and litres every year alongside your emissions. It shows whether you are really using less, and the estates and fleet managers who do the work will recognise their own bills in it.
Separate your actions from the grid. Say in your report how much of any fall in Scope 2 came from the new factor and how much from using less. The Government's guidance for the public sector makes the same point.
Decide how to treat past years. DESNZ does not normally revise earlier factors, and leaves it to you whether to apply the new ones to past years. Whichever you choose, explain it in your method note.

What this site uses

The carbon calculator on this site and the baseline workbook in the free templates both use the 2026 factors: 0.18231 kgCO2e per kWh for natural gas (gross calorific value), 0.13096 for UK electricity and 0.01299 for electricity lost in the grid. The next set is expected in June 2027, and both will be updated then. Sign up below and you will hear when they are.

Sources

Rules and figures checked in November 2026. They change, so check the current version before you rely on them.