Emissions from electricity use
Preview Version 0.1.0Estimate the CO₂ and other greenhouse gases from a year of electricity use at your eGRID subregion's average rates.
CO₂
332.87metric tons
1,000 MWh in ERCT is about 332.87 metric tons of CO₂. With other gases, it is 334.14 tons of CO₂e (eGRID2023).
EPA · NIST SP 811Cross-checked · A worked example and the spec's 800 lb/MWh case (362.87 metric tons for 1,000 MWh) pass. CO₂e computed from each subregion's CO₂, CH₄, and N₂O rates with the technical guide's GWPs matches eGRID's own published CO₂e rate within 0.1% in all 27 subregions. What this means
Example values · Review pending Report a problem
How we got this
Method
Multiply the energy by the subregion's eGRID2023 total output emission rate for each gas (lb/MWh), convert pounds to metric tons (0.45359237 kg/lb), and add CH₄ and N₂O to CO₂ with the 100-year global warming potentials eGRID uses (AR5: 28 and 265).
Steps
- eGRID2023 total output emission rates for ERCT: 733.862 lb/MWh CO₂, 0.043 lb/MWh CH₄, 0.006 lb/MWh N₂O.
- CO₂: 1,000 MWh × 733.862 lb/MWh × 0.45359237 kg/lb ÷ 1,000 = 332.87 metric tons.
- CO₂e: CO₂ + 28 × CH₄ + 265 × N₂O = 334.14 metric tons (AR5 100-year GWPs, as eGRID uses).
- These are annual average rates for every hour of the year. With interval data, hourly rates give a better answer, because the grid's mix changes hour by hour.
Constants
- 1 lb = 0.45359237 kg (exact). NIST SP 811, exact by definition
- 733.862 lb CO₂/MWh (ERCT) (average, 2023). EPA eGRID2023, subregion total output emission rate
Assumptions
- The subregion's average rate over the whole year applies to every MWh, whenever it was used (location-based accounting).
- Total output rates include all generation in the subregion; they are not marginal or hourly rates.
Sources
- EPA, Emissions & Generation Resource Integrated Database (eGRID2023), eGRID2023, served snapshot 2026-10, Subregion file: total output emission rates (lb/MWh) for CO₂, CH₄, N₂O, and CO₂e
- EPA, eGRID2023 Technical Guide, January 2025, CO₂ equivalent emissions, PDF page 23: GWPs from AR5 without climate-carbon feedbacks (CH₄ 28, N₂O 265)
- NIST Special Publication 811, 2008, Appendix B.8, pound (avoirdupois) to kilogram
Known limits
- Average annual rates miss the hour-by-hour changes in the grid's mix; use hourly data when you have it.
- This is location-based accounting; contracts for clean power (market-based accounting) are not reflected.
- Rates are eGRID2023's; a newer edition will change them.