Energy Calculations
From Green Needham



This page contains reference information on calculations, units and definitions used in energy applications  heating, cooling, etc.
BTUs and Conversion
The best way to compare difference sources of energy is to convert each to BTUs. Note that the BTU content of fuels varies from country to country. This data from the EIA uses the average energy content of the respective fuels as used in the US.
 1 barrel (42 gallons) of crude oil = 5,800,000 BTU
 1 gallon of gasoline = 124,000 BTU
 1 gallon of diesel fuel = 139,000 BTU
 1 gallon of heating oil = 139,000 BTU
 1 barrel of residual fuel oil = 6,287,000 BTU
 1 cubic foot of natural gas = 1,031 BTU
 1 therm of natural gas = 100,000 BTU
 1 therm = 97 cubic feet
 1 gallon propane = 91,000 BTU
 1 short ton of coal = 20,754,000 BTU
 1 kwh of electricity = 3,412 BTU
Natural Gas
 1 cubic foot = 1,031 BTU
 1 therm = 100,000 BTU = 97 cubic feet
Heating and Cooling
 1 Ton of cooling capacity = 12,000 BTUs (/hour)
Cooling for Computer Systems
 1 watt = 3.4 BTU/h
 1000 BTU/h = 293W
 EER
 Energy Efficiency Rating  efficiency rating of equipment at a specific external and internal temperature
 SEER
 Seasonal Energy Efficiency Rating  EER calculated over a range of temperatures (usually those prevailing at a location where the test is done)
 COP
 Coefficient of performance (units of cooling per unit of work)
 SEER = BTU / Watthours
 SEER = COP * 3.792
 SEER = EER / 0.9
 EER = COP * 3.413
 1 BTU = heat given off by a kitchen match
 AFUE  Annual Fuel Utilization Efficiency  % of fuel used that heats the home (balance wasted up flue)
 Air Conditioner = 20 BTU/sq ft of space (eere.energy.gov  Room AC)