Electric C02e factors are pulled annually from the EPA's published emissions documents. Updates are usually done in January and are current to the two years prior. Example: January 2025 carbon factors will be updated with verified data through 2023. https://www.epa.gov/egrid/download-data. Electric C02e rates are assigned per eGRID region.
District chilled water is calculated based on eGRID electric C02e rates with an assumed chiller efficiency of 4.7 COP.
Onsite combustibles (fuel oil, propane, coal, steam, wood, etc.) emissions are based on published emission factors from ENERGY STAR. http://portfoliomanager.energystar.gov/pdf/reference/emissions.pdf. Those factors are not eGRID specific but are updated annually.
Electric - lbs./MWh
Gas and Steam - lbs./MMBtu
Chilled Water - lbs./Ton Hour
Because there are three different units, B3 converts to kBtu.
kBtu x carbon factor = C02e
B3 Benchmarking Potential Savings is the actual kBtu less the benchmark kBtu.