Questions people ask about emission factors, answered

31 guides, each titled as the question it answers, with the answer in the first paragraph and every number pinned to a data version. Grouped by what you are trying to do.

31 guides · 7 groups · every figure sourced

Choosing

Comparison

7 guides

Which API, database or vendor — decided on licence, provenance and price, with the tests to run yourself.

Build vs Buy: The Emission-Factor Layer Is there an open-source or cheaper alternative to commercial carbon data APIs? What API should I use to get emission factors? What are the alternatives to Climatiq for emission factor data? What are the best free sources of greenhouse gas emission factors? Where do I source the emission factors for a freight calculator? Which emission factor database should I use in 2026?

Doing

Tutorial

8 guides

Emission factors in Python, JavaScript, SQL, a spreadsheet or an agent, on cited values pinned to a data version.

Calculate Carbon Emissions in JavaScript Carbon Accounting in the Data Warehouse Emission Factor Version Control Emission Factors in Google Sheets & Excel Emission Factors in LangChain Agents How do I get DEFRA conversion factors into my software automatically? How do I get the UK electricity emission factor in Python? How do I stop an LLM inventing emission factors in my product?

Looking up

Reference

5 guides

What you may republish, how to cite a factor, which fuel factor you need, and where AI is reliable.

Where AI Is Reliable on Emission Factors — and Where It Isn’t Where can I download emission factors as a dataset I can use commercially? Where do audit-grade emission factors and their citations come from? Which emission factor datasets can I legally redistribute in a product? Which Fuel Emission Factor Do You Need?

Complying

Regulation

4 guides

CBAM default values, DEFRA conversion factors and the other regulated numbers, as they stand this year.

DEFRA Conversion Factors 2026: Every Change, Diffed For CSRD reporting, which emission factor source should we standardise on? What data do I need for PCAF financed emissions reporting, and where from? Where do I get CBAM default values for a system?

Understanding

Methodology

3 guides

Why published factors disagree, what a traceable number is made of, and what AR7 will change.

Anatomy of a Traceable Carbon Number IPCC AR7: What Will Change, and Why Nobody Can Tell You When Why Emission Factors Disagree

Evidence

Research

3 guides

Our own measurements: how accurate AI is on emission factors, and which providers it recommends.

How Accurate Is AI on Emission Factors? 467 Questions, 5 Models How Often Do Emission Factors Actually Change? Which Carbon Data Providers Do AI Models Recommend?

Getting Started with Carbon Accounting

Getting Started with Carbon Accounting

1 guide
15 Sustainability Quotes on Measurement, Honesty, and the Future We Owe
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