DEFRA published its 2026 greenhouse gas conversion factors on 11 June 2026. The headline change: UK grid electricity is now 26% less carbon-intensive than a year ago. Here's what changed, what stayed the same, and which year's factors you should be using.

Note: requirements change. Last reviewed August 2026 — always check the current guidance for your specific tender or obligation.

Every June, DEFRA and DESNZ publish updated greenhouse gas conversion factors for UK organisations. The 2026 edition landed on 11 June 2026, and for any business that uses electricity, the headline number has shifted materially: the UK grid is now substantially cleaner, and your Scope 2 figure should reflect that.

This post covers the key changes for the factors most businesses encounter in practice — electricity, natural gas, and transport — and explains the rule that catches many companies out: which year's factors to actually use.

The biggest change: UK grid electricity is 26% cleaner

The location-based grid electricity factor for 2026 is 0.131 kgCO₂e per kWh, down from 0.177 kgCO₂e/kWh in 2025. That's a 26% reduction in a single year — the largest single-year fall in recent memory.

To put it in practical terms: if your business consumed 100,000 kWh of electricity last year, your Scope 2 grid electricity figure has fallen from roughly 17.7 tonnes CO₂e (at 2025 factors) to 13.1 tonnes CO₂e (at 2026 factors) — even with identical consumption.

The driver is grid decarbonisation. Higher renewable generation and reduced gas-fired power have cut the carbon intensity of every unit drawn from the national grid. UK grid intensity has fallen by more than 65% since 2012 — and 2026 marks another significant step in that trajectory.

What this means for your reporting

If you use the location-based method for Scope 2 (the most common approach for UK businesses), your 2026 electricity emissions will be meaningfully lower than 2025's — even if your consumption hasn't changed. Year-on-year comparisons need context: a drop in Scope 2 this year may reflect a cleaner grid, not a reduction in energy use. It's worth separating the two effects when communicating progress to stakeholders.

If you use the market-based method — backed by renewable energy certificates such as REGOs — you may already be reporting near-zero Scope 2 from electricity. The location-based factor is still relevant for your Scope 2 location-based disclosure, since the GHG Protocol recommends reporting both.

Natural gas: broadly stable

The combustion factor for natural gas in 2026 is 0.18231 kgCO₂e per kWh (GCV basis) — a marginal change of less than 0.5% from 2025. By volume, that's approximately 2.026 kgCO₂e per cubic metre.

Natural gas is the primary source of Scope 1 emissions for most office-based and light-industrial businesses in the UK. Unlike electricity, the carbon content of gas is determined by its chemical composition, which changes slowly. Unless you've reduced gas consumption or switched to alternatives — heat pumps, biomethane — your gas-related Scope 1 figures will look similar to last year.

One thing to note: the combustion factor covers only the on-site burning of gas. There's an additional upstream factor for the extraction, processing, and transport of gas to your meter — this sits in Scope 3 Category 3 (fuel and energy-related activities). That factor is in the DEFRA tables and should be included in a complete footprint. See all 15 Scope 3 categories explained for context.

Transport: modest changes

Road transport emission factors in 2026 show minimal year-on-year movement. The updates reflect gradual changes in fleet composition assumptions and improving average vehicle efficiency as older vehicles retire and EVs enter the mix in greater numbers.

For carbon reporting purposes, if your Scope 1 company vehicle emissions were calculated last year using the same methodology, applying 2026 factors to 2026 actuals will produce comparable figures — the factors haven't shifted materially.

Air travel factors are similarly stable. UK domestic, short-haul, and long-haul factors remain in a similar range to 2025. If you apply radiative forcing uplift to business flights (recommended by many practitioners to capture non-CO₂ warming effects), the multiplier is broadly unchanged.

The rule that trips companies up: which year's factors to use

DEFRA publishes factors annually, and each edition covers the year of your data — not the year of publication. The 2026 factors, published in June 2026, are the correct factors for 2026 activity data.

If you're calculating your 2025 footprint — perhaps for a year-end report, a Carbon Reduction Plan, or a SECR disclosure — you should use the 2025 DEFRA factors, not the 2026 ones.

This trips businesses up in two directions:

Using the most recent factors regardless of the data year. A business calculating its calendar-year 2025 footprint in late 2026 should still use 2025 factors. Applying 2026 factors would produce a lower electricity figure that reflects the 2026 grid — not the grid that was actually supplying power in 2025.
Not updating factors when they should. Conversely, if you're calculating your 2026 footprint as the year progresses, the 2026 factors are the right ones — using last year's tables would overstate your Scope 2 by roughly a third.

The discipline is straightforward: match the factor year to the data year. Keep the previous year's DEFRA tables accessible alongside the current edition so you can apply each correctly when you need them.

DEFRA factors and the GHG Protocol

The DEFRA/DESNZ conversion factors are designed for use with the GHG Protocol Corporate Standard and SECR reporting in the UK. They're the authoritative source for Scope 1, Scope 2, and many Scope 3 calculations — from energy and transport to waste and water.

One area where DEFRA factors aren't the primary source: Scope 3 Category 1 (purchased goods and services). For spend-based estimates of supply chain emissions, economy-wide input-output emission factors from databases such as EXIOBASE are typically used. We cover that method in how to calculate Scope 3 from spend data.

Keeping factors current without manual tracking

For businesses using a spreadsheet, updating factors each June is a manual step that's easy to miss or delay. The risk is calculating live 2026 emissions against 2024 or 2025 factors — which will overstate Scope 2 by a significant margin given the size of this year's electricity change.

SpendToScope updates its factor library each year when DEFRA publishes, and applies the correct year's factors to the correct data automatically. If you're reporting on a rolling basis, the system matches activity dates to the right factor vintage — so your Scope 1 and Scope 2 numbers are always on the current basis without a manual update step.

Key numbers at a glance

UK grid electricity, location-based (Scope 2): 0.131 kgCO₂e/kWh — down 26% from 0.177 in 2025
Natural gas combustion (Scope 1, GCV): 0.18231 kgCO₂e/kWh (~2.026 kgCO₂e/m³)
Road transport and air travel: broadly stable year-on-year
Factor year rule: match the factor year to the data year — 2026 factors for 2026 data, 2025 factors for 2025 data
Publication date: 11 June 2026 (DEFRA/DESNZ)

DEFRA Emission Factors 2026: What Changed and What It Means for Your Carbon Footprint