Emissions Factors Toolkit

Overview

The Emissions Factors Toolkit (EFT) is published by Defra and the Devolved Administrations to assist local authorities in carrying out Review and Assessment of local air quality as part of their duties under the Environment Act 1995 as amended by the Environment Act 2021.

The EFT allows users to calculate road vehicle pollutant emission rates for NO_x, PM₁₀, PM_2.5 and CO₂ for a specified year, road type, vehicle speed and vehicle fleet composition.

The EFT is updated periodically due to updates to underlying data including vehicle fleet composition and emissions factors. Users are therefore advised to check this page regularly to ensure they are using the most up to date version of the tool for their studies.

Current Version

Documents

EFT_2026_v15.0

Released: October 2026 (XLSB, 5.9 MB)

EFT v15.0 User Guide

Released: October 2026 (PDF, 2.6 MB, 55 pages)

Details

The current version of the EFT is Version 15.0.

The accompanying EFT User Guide explains in detail the methodology, datasets and assumptions used in the development of the EFT. It consolidates previously available information and guidance on the use of the EFT, and provides information regarding previous versions (changes and updates).

Version 15 comprises a number of updates relative to v14.2, with the most significant changes being summarised below.

• Update of the Base Fleet Splits up until 2050. The fleet composition projections included in the tool outside of London have been updated in line with the projections developed from the 2024 version of the the National Atmospheric Emissions Inventory (NAEI)[1] programme in May 2026. This used information provided by DfT in December 2025 on future sales and activities of new petrol, diesel and electrically-powered cars and LGVs, combined with future forecasts in traffic (vehicle kilometres) including other vehicle types from DfT’s National Transport Model.
• The factors used in the calculation of f-NO₂ have been validated as reflecting the latest factors used in the NAEI [1].
• The factors used to convert Energy Consumption to CO₂ emissions have been reviewed and updated to bring them into line with the May 2026 update of the EMEP/EEA Air Pollution Emission Inventory Guidebook 2023[2].

The full timeline of EFT update details is provided in the EFT User Guide.

A list of the data sources used for the development of the current EFT is provided in Appendix D: Data Sources.

[1] https://naei.energysecurity.gov.uk/

[2] https://www.eea.europa.eu/en/analysis/publications/emep-eea-guidebook-2023/part-b-sectoral-guidance-chapters/1-energy/1-a-combustion/1-a-3-b-i/@@download/file

Previous Version

Documents

EFT v14.2

Released: September 2026 (XLSB, 5.8MB)

EFT v14.2 User Guide

Released: September 2026 (PDF, 2.56MB, 56 pages)

EFT v13.1

Released: March 2025 (XLSB, 5.17 MB)

EFT v13.1 User Guide

Released: March 2025 (PDF, 2.43MB, 47 pages)

EFT v13

Released: March 2025 (XLSB, 5.79 MB)

EFT v13 User Guide

Released: March 2025 (PDF, 2.43MB, 51 pages)

Details

Whilst local authorities are advised to use the latest version of the EFT for all future work, in support of ongoing work, the previous version of the EFT has been provided.

For older versions of the EFT please contact the LAQM Helpdesk for further assistance.