Energy Calculations

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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 / Watt-hours
  • SEER = COP * 3.792
  • SEER = EER / 0.9
  • EER = COP * 3.413


Wikipedia Article


  • 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)