Emission factors guide: India grid, CEA, DEFRA, IPCC and IEA
Emission factors convert activity data, such as litres of diesel or kilowatt-hours of electricity, into greenhouse gas emissions, and the factor you choose can move a figure as much as the data itself. For Indian companies, the India grid emission factor for Scope 2 normally comes from the Central Electricity Authority's CO2 baseline database, while fuels, transport and Scope 3 draw on IPCC defaults, DEFRA/DESNZ, the IEA or supplier-specific data. Whatever the source, record the version used, so that every figure can be reproduced and compared year on year.
What emission factors are
An emission factor is a coefficient: emissions per unit of activity. A typical calculation is:
Emissions (tCO2e) = activity data × emission factor, with each gas converted to CO2 equivalent using its global warming potential (GWP).
Factors exist for combustion (per litre, tonne or GJ of fuel), electricity (per kWh), transport (per tonne-km or passenger-km), materials (per tonne), waste treatment and spend (per unit of currency). They differ by gas, by technology and by geography, and most are revised regularly. That is why a careful inventory treats emission factors as data in their own right, with a source, a version and a validity period.
The main sources of emission factors
| Source | What it covers | Best used for | Update cycle |
|---|---|---|---|
| CEA CO2 baseline database (India) | Emission factors for the Indian grid: weighted average, operating margin, build margin, combined margin | Location-based Scope 2 for grid electricity in India | Roughly annual, as numbered versions |
| IPCC Guidelines and Emission Factor Database | Default factors for fuels, industrial processes, agriculture, land use and waste | Scope 1 combustion and process emissions where no national factor exists | 2006 Guidelines with the 2019 Refinement; database updated over time |
| UK DESNZ (formerly DEFRA) conversion factors | Fuels, electricity (UK), refrigerants, transport, travel, materials, waste, hotel stays | Transport, travel, refrigerants and waste where no local factor is available | Published annually, usually around June |
| IEA emissions factors | Electricity and heat factors by country | Scope 2 for overseas sites without an official national factor | Annual, under licence |
| National inventories and regulators | Country-specific fuel and process factors | Reporting under a national scheme, such as CCTS or CBAM monitoring rules | Varies |
| Supplier-specific and product data | Factors from suppliers' own inventories, EPDs or product footprints | Purchased goods and market-based Scope 2 from contractual instruments | As supplied |
| Environmentally extended input-output (spend) factors | Emissions per unit of spend by sector | Screening Scope 3 and filling gaps | Varies by model |
The India grid emission factor and the CEA CO2 baseline database
The Central Electricity Authority, under the Ministry of Power, publishes the CO2 Baseline Database for the Indian Power Sector. It was first developed for Clean Development Mechanism projects and is calculated with the CDM tool for grid emission factors. It reports several factors for the integrated national grid:
- Weighted average emission factor — total CO2 from grid-connected generation divided by total net generation, including renewables. This is the factor normally used for location-based Scope 2 in corporate inventories and BRSR GHG emissions.
- Operating margin — reflects the generation that would be displaced at the margin by a new project.
- Build margin — reflects the most recently built capacity.
- Combined margin — a weighted blend of operating and build margins, used to estimate baseline emissions for carbon credit projects. It is not a Scope 2 factor.
CEA releases a new version roughly once a year, covering the latest fiscal year, sometimes on provisional data. As an example, Version 20.0, released in December 2024, put the weighted average for FY 2023-24 at 0.727 tCO2/MWh. Versions 21.0 and 22.0 followed in 2025 and 2026, covering later fiscal years. Over the long run the weighted average has trended down as renewable generation grows, although it can rise in individual years. Always take the value from the current CEA publication rather than a secondary source, and note which version you used.
Two practical points for India:
- Timing. A version for your reporting year may not be available when you close your books. Decide in your methodology whether you use the latest available version and true up later, or the version matching the year, and apply it consistently.
- Captive and open access power. Electricity from your own captive plant is Scope 1 (fuel burned on site), not Scope 2. Renewable power bought through open access or backed by renewable energy certificates affects the market-based Scope 2 figure, not the location-based one. Our guide to location- vs market-based Scope 2 covers this.
DEFRA emission factors and other international sets
The UK government's greenhouse gas conversion factors, now published by the Department for Energy Security and Net Zero (DESNZ) and still widely called DEFRA emission factors, are free, broad and well documented. They are popular in India for business travel, freight, refrigerants and waste because Indian national factors do not exist for many of these activities. The 2026 set was published in June 2026.
Use them with care. UK electricity factors describe the UK grid and should never be used for Indian electricity. Some transport factors reflect UK vehicle fleets and load factors. Where a factor is clearly country-specific, look first for an Indian or regional alternative, and note the choice in your methodology.
For fuels, IPCC default factors, based on carbon content and calorific value, are the common fallback. Where you hold a fuel's measured calorific value or carbon content, as many CCTS and CBAM installations do, a plant-specific factor is more accurate and is often expected.
How to choose an emission factor
A simple hierarchy works for most inventories:
- Measured or supplier-specific data — your own fuel analysis, a supplier's verified product footprint or a contract-specific electricity factor.
- National official factors — CEA for Indian grid electricity; any factors prescribed by the scheme you report under.
- Recognised international sets — IPCC, DESNZ, IEA, chosen for geographic and technological fit.
- Spend-based factors — for screening and gaps, with a plan to replace them.
Check each candidate against the same tests: does it match the geography, technology and year of the activity; are the gases and GWP basis consistent with the rest of your inventory; is the unit right; and does it include or exclude upstream emissions in the way your boundary requires? Frameworks such as IFRS S2 point to GWP values from the latest IPCC assessment, so mixing factors built on different GWP sets should be avoided or adjusted.
Why emission factor versioning matters
Factors change every year, and the changes can be large. If a factor set is overwritten in place, last year's reported emissions quietly change, and nobody can explain why. Versioning prevents that:
- Reproducibility. Assessors and verifiers for BRSR Core, CCTS and ISO 14064-3 will recalculate figures. They need the exact factor and version.
- Trend analysis. A fall in Scope 2 may come from lower consumption or a cleaner grid factor. You can only tell them apart if both versions are on record.
- Base-year recalculation. When a methodology changes significantly, targets and base years may need restating. That requires knowing which factors produced the original numbers.
- Consistency across reports. BRSR, CDP, customer questionnaires and CBAM should use the same approved figures, not a different calculation each time.
Illustrative: a site using 10,000 MWh a year reports 7,270 tCO2 at 0.727 tCO2/MWh. If the next CEA version is applied to the same consumption, emissions fall without any action by the site. Disclose that as a factor change, not as a reduction achieved.
How EKOTRACE helps
EKOTRACE holds emission factors as versioned records with their source, year and validity, whether they are CEA grid factors for India or international sets for fuels, transport and materials. Each calculated figure stores the factor version used, so it can be reproduced at any time, and new versions are applied from a chosen date without changing approved history. Scope 2 is calculated on both location- and market-based methods, and supplier-specific factors from the supplier portal can replace averages as they arrive. See GHG accounting, supplier engagement and our guide to carbon accounting software in India.
Frequently asked questions
What is the grid emission factor for India?
The official source is the Central Electricity Authority's CO2 baseline database, which publishes a weighted average emission factor for the national grid each year. Version 20.0 gave 0.727 tCO2/MWh for FY 2023-24, and later versions have been published since. Check the current CEA release for the value applicable to your reporting year.
Can Indian companies use DEFRA emission factors?
Yes, for activities where no suitable Indian factor exists, such as many transport, travel, refrigerant and waste categories. They should not be used for Indian grid electricity, which should use CEA factors. Document the choice in your methodology.
Should I use the combined margin or the weighted average for Scope 2?
Use the weighted average for location-based Scope 2 in a corporate inventory. The combined margin is designed for estimating baseline emissions of carbon credit projects.
How often should emission factors be updated?
Review them at least once a year, when major sets such as CEA and DESNZ publish new versions. Apply updates from a defined date, keep the old versions on record, and disclose material effects of factor changes on your reported trend.