Short Answer: MAISY RECS Database GHG emissions are calculated with EPA factors that convert consumption of each fuel to a CO2e equivalent.
Longer Answer: The EPA publishes CO2e equivalents for each fuel type (electricity, natural gas, etc.) for various geographic US regions. Carbon dioxide equivalents (CO2e) incorporate all other greenhouse gas warming equivalents within the CO2e measure to provide a single global warming metric.
The MAISY RECS Extended Hourly Load Databases access either ZIP-level or state-level CO2e emissions data for each RECS customer depending on geographic detail of the EPA databases and RECS customer geolocation. RECS customers are geo-located with the 30-year heating and cooling degree day variables in each RECS record to the closest ZIP code tabulation area.