UK GHG Conversion Factors: What the 2026 Updates Mean for your Reporting

The UK Government’s greenhouse gas conversion factors are one of the most widely used tools for UK organisational carbon reporting. Published annually, they enable the conversion of consumption data into greenhouse gas (GHG) emissions.

In this blog, we cover two key UK emission factor databases that are commonly used and free to access: the activity-based conversion factors published by the Department for Energy Security and Net Zero (DESNZ), and the spend-based emissions multipliers published by the Department for Environment, Food and Rural Affairs (DEFRA).

The latest releases in 2026 are the 2026 DESNZ conversion factors and the 2023 spend-based emissions multipliers. They are particularly important because they include significant methodological and data updates, which will affect reported emissions even where a business has not made any operational changes. For reporting teams, it is essential to understand how this affects your year-on-year GHG emissions comparisons.

What are the DESNZ conversion factors and DEFRA spend-based emissions multipliers?

The 2026 DESNZ conversion factors enable organisations to calculate emissions from operational activity data, such as fuel use, electricity purchased, distance travelled, or refrigerant losses. To create these, DESNZ combines the latest UK emissions data, energy statistics and scientific methodologies to calculate standardised emission factors that convert activity data into CO₂ equivalent, updating them annually to reflect real-world changes.

Companies should use the year of publication that matches their reporting year. The factors are primarily intended for UK-based organisations and international organisations reporting on UK operations, but because the dataset is so complete, it is often used as a proxy for international organisations to report emissions outside of the UK.

DEFRA’s 2023 spend-based emissions multipliers estimate emissions from expenditure, providing an initial assessment of supply chain emissions based on the purchase of different goods and services. Multipliers are provided by UK COICOP (which classifies household spending) and SIC codes (which classify businesses by their economic activity), so spend categories or spend with suppliers will need to be mapped against these. The multipliers lag by a few years because they are derived from national input-output economic accounts and environmental datasets, which take a few years to compile and validate before emission factors can be produced.

They also reflect spend in the year they relate to, so make sure your calculations factor in price changes by adjusting for inflation over the cumulative years. For example, if you are reporting for 2026, you will use the 2023 spend-based multipliers and adjust them in line with three years of inflation. For businesses, SIC codes are typically more applicable, as COICOP classifies household spending. It is also important to know that spend data used in emissions calculations should exclude VAT when using SIC code multipliers.

Spend-based calculations are a useful starting point for screening Scope 3 supply chain emissions. However, organisations should progressively improve data quality by replacing spend assumptions with activity-based, product-level or supplier-specific emissions data wherever feasible.

Significant updates in the conversion factors

Factors are updated annually to reflect the latest data and methodology changes. Here are the significant changes to the 2026 DESNZ GHG conversion factors, compared to the previous year, that anyone working in emissions reporting should be aware of:

• UK location-based electricity: a 26% year-on-year reduction, the most significant change in the whole 2026 factor dataset. This is largely due to a methodological update that reduces the data lag from two years to one, meaning the release captures two years of grid mix and grid loss improvements compared with the previous publication. The change also reflects continued grid decarbonisation, including increased renewable generation and reduced reliance on natural gas. Factors that rely heavily on grid electricity are also affected, including those below.
• Transmission and distribution losses: a 30% reduction, primarily driven by the emission factor updates for UK electricity, but also by changes in grid losses and revised accounting of electricity imports and exports.
• Business travel: the international rail emissions factor sees a 156% increase, because it now reflects post-pandemic service patterns and updated assumptions about rolling stock use. Coach travel factors rose by 43% after more detailed operational data from major operators replaced outdated occupancy assumptions. London Underground emissions fell by 45% due to cleaner grid electricity and updated passenger data, while national rail emissions decreased by 13% following revisions to fleet composition and passenger usage.
• Passenger and delivery vehicles: many vehicle factors have moved up or down depending on the latest data on efficiency improvements, vehicle usage patterns, fuel economy, energy use, and changes to the electricity grid emission factors.
• Homeworking: a 31% reduction in office equipment factors reflects methodological updates to the electricity factors. This factor had not been updated since 2022, so the reduction also captures several years of decreasing grid emissions.
• Refrigerants: one refrigerant factor, R-511A, has risen by 100% due to methodological revisions.

DEFRA’s spend-based emissions multipliers have also been released and updated. As well as changes to specific factors, there are several things to note:

• Each annual update brings restatements to previous years due to amendments in the underlying data and methodological improvements. When comparing spend-based emissions across years, you should therefore use the latest, restated multipliers for the associated year(s).
• Comparing the 2023 SIC multipliers with the restated 2022 values, 101 categories fell and 11 rose.
• The largest decreases include “Information services” by 28%, “Other mining and quarrying” by 26%, “Crude petroleum and natural gas” by 23%, and “Water transport” by 20%.
• The largest increases include “Other basic metals and casting” by 60%, “Forestry and logging” by 36%, “Mining support services” by 15%, and “Remediation and waste management” by 12%.
• You should look at your top spend categories to see how these specifically have changed.

Why this matters for company reporting

Conversion factor updates can affect reported emissions independently of operational performance. A company may report reduced or increased emissions without any movement in underlying consumption or activity. There is a risk of false interpretation of emissions data movements if businesses present year-on-year reductions without explaining the cause.

For the latest updates, businesses with large electricity consumption, electric fleets, international rail travel or homeworking emissions may see noticeable changes in their reported footprint, but this does not necessarily mean the organisation has reduced consumption or improved performance. For example, Scope 2 emissions may reduce without a reduction in kWh consumed, or a supplier’s emissions may fall with no change in spend. Organisations should distinguish between changes driven by operational improvements, activity levels, data quality, methodology and updated factors. Responding beyond headline emission figures by tracking energy, travel and other operational drivers, and making decisions based on this, will support operational savings in the long run and reduce the risk of relying on system changes for decarbonisation.

If you are relying on spend-based data for Scope 3 supply chain emissions reporting, your reported emissions will depend solely on the multipliers’ values and your spend, rather than on emissions from suppliers. This will be particularly noticeable for growing organisations whose spend is also rising. So if you want to understand your supply chain emissions accurately, and have agency in influencing and demonstrating emission reductions, gathering supplier- or product-specific emissions data is key.

Clear explanations are also important for governance and stakeholder confidence. SECR and ESOS already require many UK companies to disclose energy consumption, and the UK Sustainability Reporting Standards, published for voluntary use in 2026, expect organisations to disclose calculation methodologies, assumptions and inputs. Strong methodology notes will help businesses prepare for more rigorous climate reporting expectations.

Actions for businesses in 2026

1. Complete your emissions calculations: for your 2026 report, use the 2026 DESNZ conversion factors for activity data and the 2023 DEFRA spend-based multipliers for spend data, remembering to adjust for inflation.
2. Recognise emissions drivers: review whether material year-on-year changes to emissions are due to updated factors or driven by business operations. Where factor changes are material, explain them transparently to key stakeholders and within your GHG emissions reports.
3. Track performance consistently: maintain clear records of emission factors, methodologies and assumptions used each year, to enable meaningful year-on-year comparisons.
4. Improve data quality: if you use spend-based emission multipliers, move towards replacing them with activity data (for example fuel consumption, energy use or mileage) or, even better, supplier-specific data (for example suppliers’ reported emissions or Environmental Product Declarations). This improves emissions reporting accuracy and better tracks decarbonisation efforts.

Whether you’re just starting your carbon reporting journey or looking to strengthen your existing approach, our carbon and climate experts can provide practical support and actionable insights to improve your emissions reporting, identify decarbonisation opportunities, and help you achieve your climate goals. If you’d like to discuss emissions calculations and decarbonisation strategies, we’d love to hear from you.