WattShed Footprint

What the saved energy kept out of the air.

Bring an annual kWh-saved figure, from the measured savings check or your own M&V, choose the eGRID subregion the home sits in, and this multiplies your figure by a published emission factor. That is the entire calculation: your number times a rate EPA publishes for that subregion's grid mix.

The factor carries a vintage because the grid mix shifts every year as generation changes. A factor from a different eGRID release will not match this one for the same subregion, and that is expected, not an error. Everything runs in this browser tab; nothing entered here is uploaded or stored.

This is an estimate for reporting context: not a certified offset, not a credit, and nothing produced here is tradable. It answers roughly how much a saved kWh figure kept out of the air, not a question any registry would sign off on.

1. Saved energy

Annual kWh saved

The energy a retrofit saved over a year, in kWh. Get this figure from the measured savings check or your own M&V.

Annual kWh saved

2. eGRID subregion

Where the home sits on the grid

eGRID reports emission factors by subregion, not by state or utility. Not sure which one covers this address? EPA's Power Profiler tool looks it up from a ZIP code: https://www.epa.gov/egrid/power-profiler.

Subregion

3. Convention

Which rate to apply

eGRID publishes two rates per subregion. Non-baseload is the standard convention for an avoided-savings claim, and is selected by default.

Avoided emissions (non-baseload)The rate for the generation most likely to respond to a change in demand. The standard convention for crediting a savings figure with avoided emissions, and the default here.

Inventory rate (total output)The average rate across everything the subregion generated all year. For accounting a fixed block of consumption, not for modeling what a change avoided.

4. Result

Enter the annual kWh saved and choose an eGRID subregion to see an avoided-emissions estimate.

5. Factors table

All 27 eGRID subregions

Every subregion's rate, both conventions, so the figure above is checkable against the source table it came from.

Subregion	Non-baseload	Total output
AKGD ASCC Alaska Grid	1,085 lb CO2e/MWh	905 lb CO2e/MWh
AKMS ASCC Miscellaneous	1,554 lb CO2e/MWh	522 lb CO2e/MWh
AZNM WECC Southwest	1,179 lb CO2e/MWh	706 lb CO2e/MWh
CAMX WECC California	961 lb CO2e/MWh	430 lb CO2e/MWh
ERCT ERCOT All	1,248 lb CO2e/MWh	737 lb CO2e/MWh
FRCC FRCC All	984 lb CO2e/MWh	785 lb CO2e/MWh
HIMS HICC Miscellaneous	1,608 lb CO2e/MWh	1,133 lb CO2e/MWh
HIOA HICC Oahu	1,765 lb CO2e/MWh	1,499 lb CO2e/MWh
MROE MRO East	1,712 lb CO2e/MWh	1,405 lb CO2e/MWh
MROW MRO West	1,789 lb CO2e/MWh	927 lb CO2e/MWh
NEWE NPCC New England	889 lb CO2e/MWh	543 lb CO2e/MWh
NWPP WECC Northwest	1,623 lb CO2e/MWh	635 lb CO2e/MWh
NYCW NPCC NYC/Westchester	978 lb CO2e/MWh	866 lb CO2e/MWh
NYLI NPCC Long Island	1,319 lb CO2e/MWh	1,189 lb CO2e/MWh
NYUP NPCC Upstate NY	912 lb CO2e/MWh	243 lb CO2e/MWh
PRMS Puerto Rico Miscellaneous	1,642 lb CO2e/MWh	1,549 lb CO2e/MWh
RFCE RFC East	1,181 lb CO2e/MWh	599 lb CO2e/MWh
RFCM RFC Michigan	1,518 lb CO2e/MWh	976 lb CO2e/MWh
RFCW RFC West	1,768 lb CO2e/MWh	916 lb CO2e/MWh
RMPA WECC Rockies	1,629 lb CO2e/MWh	1,043 lb CO2e/MWh
SPNO SPP North	1,905 lb CO2e/MWh	868 lb CO2e/MWh
SPSO SPP South	1,482 lb CO2e/MWh	876 lb CO2e/MWh
SRMV SERC Mississippi Valley	1,149 lb CO2e/MWh	742 lb CO2e/MWh
SRMW SERC Midwest	1,831 lb CO2e/MWh	1,249 lb CO2e/MWh
SRSO SERC South	1,392 lb CO2e/MWh	846 lb CO2e/MWh
SRTV SERC Tennessee Valley	1,676 lb CO2e/MWh	903 lb CO2e/MWh
SRVC SERC Virginia/Carolina	1,293 lb CO2e/MWh	596 lb CO2e/MWh

Source: EPA eGRID Summary Tables 2023 Rev2 (eGRID2023rev2), cross-checked against the ENERGY STAR Portfolio Manager technical reference.

Two conventions

eGRID publishes two rates. They answer different questions.

Non-baseload: what a change avoids

eGRID's non-baseload rate estimates the emissions from the generation most likely to ramp up or down in response to a change in demand, the plants a savings retrofit actually displaces rather than the baseload fleet that runs regardless. It is the standard convention for crediting a savings figure with avoided emissions, and it is the default here.

Total output: what a subregion generates

The average emissions rate across every megawatt-hour a subregion generated over the year, baseload and non-baseload together. It answers a different question, what rate to assign to a fixed block of consumption, not what a change in that consumption avoided. Useful for inventory-style accounting, not for an avoided-savings claim.

eGRID reissues both rates yearly as the grid's generation mix shifts. This tool uses the vintage shown beside the factor below; a figure computed from an older or newer eGRID release will differ for the same subregion and the same saved-kWh number.