Most kWh-to-CO₂ calculators use a single national average (0.386 kg CO₂e/kWh for the US). That's wrong by up to 6x depending on where you are. A kWh in upstate New York (0.110 kg) produces one-sixth the emissions of a kWh in Puerto Rico (0.702 kg).
This calculator uses EPA eGRID subregion-level data, resolved to your ZIP code, for location-accurate results. Preliminary eGRID2024 factors are also available via the API with ?year=2024 - see the API docs.
The US grid is not uniform. Some regions are dominated by hydropower and nuclear (low emissions), while others rely on coal and natural gas (high emissions). Using a national average hides this variation and produces inaccurate Scope 2 numbers.
| Location | Subregion | CO₂e (kg/kWh) | 10,000 kWh = |
|---|---|---|---|
| Upstate New York | NYUP | 0.110 | 1,101 kg |
| San Francisco | CAMX | 0.195 | 1,950 kg |
| Chicago | RFCW | 0.416 | 4,155 kg |
| Houston | ERCT | 0.334 | 3,341 kg |
| Miami | FRCC | 0.356 | 3,560 kg |
| Long Island | NYLI | 0.539 | 5,395 kg |
| Honolulu | HIOA | 0.680 | 6,799 kg |
Same 10,000 kWh, 6x difference in emissions. Source: EPA eGRID2023 Rev 2.
If you need to do this calculation in code (for an app, report, or pipeline), use the /api/calculate endpoint:
curl -X POST "https://emission-factors.com/api/calculate" \
-H "Content-Type: application/json" \
-d '{"zip": "94105", "kwh": 50000}'
# Response:
# { "candidates": [{ "subregion": "CAMX",
# "co2e_kg": 9751.85,
# "co2e_lb": 21499.15 }] }Or get the raw emission factor and do the math yourself:
curl "https://emission-factors.com/api/lookup?zip=94105"
# → co2e_kg_per_kwh: 0.195037
# Your calculation: 50,000 kWh × 0.195037 = 9,751.85 kg CO₂eFree, no key, no signup. All endpoints included.
Read the API docs →?year=2024 (Cornerstone Data, CC-BY-4.0)emission-factors.com is an independent service. Not affiliated with the EPA. Terms · Privacy · Full subregion table