Factor API: official UK and country emission factors for your software

How it works

1. Sign in and open Factor API in the app. Create a key and copy it (it is shown once).
2. Send it with each request as Authorization: Bearer crf_….
3. Read data, and show the attribution text wherever the figures appear.

curl -H "Authorization: Bearer $FACTOR_API_KEY" \
  "https://carbonrecycling.co.uk/api/v1/uk/factors?year=2026&q=diesel&category=fuels&scope=1"

Keys are kept on your server, not in a web page. The API is read-only (GET), answers in JSON, allows cross-origin requests, and is versioned: anything that would break your code goes in a new version, not into v1.

Endpoint reference

Base address https://carbonrecycling.co.uk/api/v1. GET /api/v1 lists the endpoints and sources without a key. For UK factors, year is the DESNZ set (2002 to 2026, default the latest). For electricity by country and US region, year is your reporting year and the answer is the latest data year up to it.

A UK factor by ID

GET https://carbonrecycling.co.uk/api/v1/uk/factors/7_400_4000_5_1?year=2026

{
  "data": {
    "id": "7_400_4000_5_1",
    "year": 2026,
    "scope": "Scope 2",
    "category": "UK electricity",
    "path": ["UK electricity", "Electricity generated", "Electricity: UK", "kWh", null],
    "description": "UK electricity › Electricity generated › Electricity: UK › kWh",
    "unit": "kWh",
    "kgCo2ePerUnit": 0.13096
  },
  "attribution": [
    {
      "source": "desnz-factors",
      "name": "UK Government GHG Conversion Factors for Company Reporting",
      "publisher": "Department for Energy Security and Net Zero (DESNZ)",
      "licence": "Open Government Licence v3.0",
      "licenceUrl": "https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/",
      "attribution": "Contains public sector information licensed under the Open Government Licence v3.0. Source: DESNZ, Greenhouse gas reporting: conversion factors."
    }
  ],
  "notice": "Figures as published by each source, supplied without warranty. Carbon Recycling is not endorsed by any of the publishers named in attribution.",
  "meta": { "year": 2026 }
}

UK electricity, with the residual mix

GET https://carbonrecycling.co.uk/api/v1/uk/electricity?year=2026

{
  "data": {
    "year": 2026,
    "locationBased": { "id": "7_400_4000_5_1", "kgCo2ePerKwh": 0.13096, "scope": "Scope 2", "description": "UK electricity › ..." },
    "transmissionAndDistribution": { "id": "13_402_4000_5_1", "kgCo2ePerKwh": 0.01299, "scope": "Scope 3", "description": "..." },
    "wellToTank": {
      "generation": { "id": "15_917_4000_5_1", "kgCo2ePerKwh": 0.03682, "scope": "Scope 3", "description": "..." },
      "transmissionAndDistribution": { "id": "15_918_4000_5_1", "kgCo2ePerKwh": 0.00359, "scope": "Scope 3", "description": "..." }
    },
    "residualMix": { "kgCo2PerKwh": 0.396, "dataYear": 2025, "period": "1 April 2025 to 31 March 2026", "basis": "UK residual fuel mix, CO2 only, ..." }
  },
  "attribution": [ { "source": "desnz-factors", ... }, { "source": "desnz-fuel-mix", ... } ],
  "notice": "..."
}

A country

recommended follows the same rule as our own reports: the country's official figure, unless Ember's is more than a year newer.

GET https://carbonrecycling.co.uk/api/v1/electricity/countries/FRA?year=2025

{
  "data": {
    "iso3": "FRA",
    "name": "France",
    "reportingYear": 2025,
    "recommended": {
      "year": 2024,
      "kgCo2ePerKwh": 0.035,
      "source": "fr-ademe-base-carbone",
      "dataset": "Base Carbone V23.6, electricity average mix (combustion at the power station)",
      "basis": "..."
    },
    "ember": { "dataset": "Ember, Yearly Electricity Data", "generationTwh": 570.1, "mixPercent": { "Nuclear": 68.8, ... },
               "years": [ ..., { "year": 2025, "kgCo2ePerKwh": 0.04145 } ] },
    "official": { "publisher": "ADEME", "years": [ ..., { "year": 2024, "kgCo2ePerKwh": 0.035 } ], ... }
  },
  "attribution": [ { "source": "ember", ... }, { "source": "fr-ademe-base-carbone", ... } ],
  "notice": "..."
}

Errors and limits

Errors come back as {"error": {"status", "code", "message"}}. 400 for a bad parameter, 401 for a missing or revoked key, 403 when Factor API is not on the account (with a link to subscribe), 404 for an unknown factor, country or endpoint, and 429 once the month's calls are used.

HTTP/1.1 429 Too Many Requests
X-RateLimit-Limit: 10000
X-RateLimit-Remaining: 0
X-RateLimit-Reset: 1793491200
Retry-After: 1080000

{
  "error": {
    "status": 429,
    "code": "monthly_limit_reached",
    "message": "This account has used its 10,000 calls for this month. The count starts again on 2026-11-01, or move to a bigger tier.",
    "limit": 10000,
    "resetsAt": "2026-11-01T00:00:00.000Z",
    "upgrade": "https://carbonrecycling.co.uk/products/factor-api"
  }
}

Licences and attribution

We only serve data whose licence allows it to be passed on in a paid product, and we keep a dated copy of each publisher's terms. Every reply lists the sources behind it with their licence and the credit to show. The figures are as published, without warranty, and none of the publishers endorses Carbon Recycling or your product.

• Department for Energy Security and Net Zero (DESNZ): UK Government GHG Conversion Factors for Company Reporting. Open Government Licence v3.0. Credit: Contains public sector information licensed under the Open Government Licence v3.0. Source: DESNZ, Greenhouse gas reporting: conversion factors.
• Defra and the University of Leeds: Spend-based emissions multipliers (UK's carbon footprint). Open Government Licence v3.0. Credit: Contains public sector information licensed under the Open Government Licence v3.0. Source: Defra, UK's carbon footprint.
• HM Revenue & Customs (HMRC) and HM Treasury: UK CBAM default values and CBAM rates. Open Government Licence v3.0. Credit: Contains public sector information licensed under the Open Government Licence v3.0. Source: HMRC, Check the default values for the Carbon Border Adjustment Mechanism (CBAM); HM Treasury and HMRC, Illustrative CBAM rates and worked example.
• Ember Energy Research CIC: Ember Yearly Electricity Data (grid intensity by country). Creative Commons Attribution 4.0 International. Credit: Contains data from Ember, licensed under CC BY 4.0 (ember-energy.org).
• US Environmental Protection Agency: EPA eGRID and GHG Emission Factors Hub (to the 2025 edition). US government work, public domain under 17 U.S.C. § 105. Credit: Source: US EPA, eGRID and GHG Emission Factors Hub. Not required by law, but we credit it.
• Environment and Climate Change Canada: Canada National Inventory Report, Annex 7 electricity intensity tables. Open Government Licence - Canada 2.0. Credit: Contains information licensed under the Open Government Licence – Canada (Environment and Climate Change Canada, National Inventory Report).
• Energy Market Authority, Singapore: Singapore Energy Market Authority grid emission factors (data.gov.sg). Singapore Open Data Licence version 1.0. Credit: Contains information from Electricity Grid Emission Factors and Upstream Fugitive Methane Emission Factor accessed on 19 October 2026 from data.gov.sg, which is made available under the terms of the Singapore Open Data Licence version 1.0 (https://data.gov.sg/open-data-licence).
• ADEME (Agence de la transition écologique), France: ADEME Base Carbone (data.ademe.fr open copy), electricity. Licence Ouverte / Open Licence 2.0 (Etalab). Credit: Source: ADEME, Base Carbone® V23.6 (data.ademe.fr, last updated 3 July 2025), Licence Ouverte 2.0.
• Department of Climate Change, Energy, the Environment and Water (DCCEEW), Australia: Australian National Greenhouse Accounts Factors (2022 to 2026 editions). Creative Commons Attribution 4.0 International. Credit: DCCEEW 2026, Australian National Greenhouse Accounts Factors, Department of Climate Change, Energy, the Environment and Water, Canberra, August. CC BY 4.0. (Earlier editions credited the same way with their own year.)
• Cornerstone Sustainability Data Initiative: Emission Factors Hub 2026 (eGRID2024 electricity, AR6 GWPs). Creative Commons Attribution 4.0 International. Credit: Emission Factors Hub 2026, Cornerstone Sustainability Data Initiative, CC BY 4.0 (doi:10.5281/zenodo.20403776).
• Department for Energy Security and Net Zero (DESNZ): Fuel mix disclosure data table (UK residual fuel mix). Open Government Licence v3.0. Credit: Contains public sector information licensed under the Open Government Licence v3.0. Source: DESNZ, Fuel mix disclosure data table.
• Umweltbundesamt (UBA), Germany: Umweltbundesamt: specific greenhouse gas emissions of the German electricity mix 1990 to 2025 (Climate Change 16/2026). Umweltbundesamt data terms: data use permitted under § 12a EGovG, with UBA named as the source. Credit: Quelle: Umweltbundesamt, Climate Change 16/2026, Entwicklung der spezifischen Treibhausgas-Emissionen des deutschen Strommix in den Jahren 1990 - 2025 (Tabelle 2). Figures converted from g to kg per kWh by Carbon Recycling.
• Ministry of Ecology and Environment (MEE) and National Bureau of Statistics, China: Ministry of Ecology and Environment and National Bureau of Statistics: national electricity CO2 emission factors 2021 to 2023. Official government notice, outside copyright under Article 5 of the Copyright Law of the People's Republic of China. Credit: Source: Ministry of Ecology and Environment and National Bureau of Statistics of China, announcements 2024 No. 12, 2024 No. 33 and 2025 No. 47 (national average electricity CO2 emission factor).
• Ministry for the Environment, New Zealand (now part of the Ministry for Cities, Environment, Regions and Transport): Ministry for the Environment (New Zealand): Measuring emissions, 2026 emission factors v2 (long-format CSV), purchased electricity. Creative Commons Attribution 4.0 International. Credit: Ministry for the Environment. 2026. Measuring emissions: A guide for organisations: 2026 emission factors (version 2). Crown copyright, licensed under CC BY 4.0.
• Ideal Postcodes (service), serving ONS Postcode Directory, Ordnance Survey and National Records of Scotland data: Postcodes.io (postcode to location lookup, Great Britain postcodes only). Open Government Licence v3.0. Credit: Contains Ordnance Survey data © Crown copyright and database right. Contains Royal Mail data © Royal Mail copyright and database right. Contains National Statistics data © Crown copyright and database right. Contains NRS data © Crown copyright and database right. Postcode lookups by postcodes.io.
• Environment Agency: Environment Agency real-time flood-monitoring API (flood warning and alert areas, current warnings). Open Government Licence v3.0. Credit: This uses Environment Agency flood and river level data from the real-time data API (Beta).
• Environment Agency: Environment Agency Risk of Flooding from Rivers and Sea, and from Surface Water (NaFRA2), present day and climate change, via the Defra WMS. Open Government Licence v3.0. Credit: © Environment Agency copyright and/or database right 2025. All rights reserved. Contains public sector information licensed under the Open Government Licence v3.0.
• Scottish Environment Protection Agency (SEPA): SEPA Flood Maps (river, coastal, and surface water and small watercourses; present day and future), open map service. Open Government Licence v3.0. Credit: ©SEPA 2025; this SEPA product is licensed under the Open Government Licence version 3.0.
• Natural Resources Wales: Natural Resources Wales Flood Risk Assessment Wales (rivers, sea, surface water and small watercourses) and flood warning areas, via DataMapWales. Open Government Licence v3.0. Credit: Contains Natural Resources Wales information © Natural Resources Body for Wales and database right. All rights reserved. Flood flow estimates are based upon FEH methodology and data, © and database right UKCEH 2015. Contains Ordnance Survey data, Crown copyright and database right. Licensed under the Open Government Licence v3.0.
• Met Office: Met Office Climate Data Portal: UKCP18 local authority projections at global warming levels (hot summer days, tropical nights, summer maximum temperature, summer and winter rainfall). Open Government Licence v3.0. Credit: Contains Met Office data licensed under the Open Government Licence v3.0. Contains OS and ONS data © Crown copyright and database right. Source: Met Office Climate Data Portal, UKCP18 local authority projections.

Not included

• Carbon Intensity API (GB electricity, live and forecast)
• Xero accounting API (the customer's own ledger)
• EXIOBASE 3 multi-regional input-output (spend factors for every country)
• IEA emission factors
• ecoinvent
• SEAI conversion and emission factors (Ireland), GHG_elec sheet (electricity 2001 to 2025)
• DESNZ's overseas electricity factors in its 2021 and earlier sets, which were built from IEA data under IEA's own licence

Their terms rule out reselling or redistributing the data, so these stay out of the API. See our data sources page for the full register.