Energy Unit Conversion

Energy from different sources is measured in different units. Power is the rate of transfer of energy. For example, electrical energy is measured in watts or kilo watts and power is measured in kilo watt hours.

This page is to help me remember these units and how to translate between them. The conversions below are approximates. This page is a work in progress.

Generic Energy Units

  • Joule  J = 0.23885 cal
    • 1MJ = .27778 kWh
  • Calorie  cal = 4.184 J
  • Watt Hour Wh = 3,600 J
  • Kilo Watt Hour kWh = 1,000 x Wh = 3,600,000 J

Generic Power Units

  • 1 Watt = 3.41BTU/h = 1Joule/sec

Electricity

  • Power   Kilowatt kW
  • Energy  Kilowatts per hour kWh

Natural Gas

  • Therm
    • Therm (EC) = 105,506,000 Joules = 29.307 kWh
    • Therm (US) = 105,480,400 Joules = 29.3001 kWh
    • Therm (UK) = 105,505,585 Joules = 29.307 kWh
  • British Thermal Unit BTU = 1,055 Joules

1 million BTU (mmBTU) = 1.054616 GJ

Oil

  • 1 Barrel = 42 US Gallons = 35 Imperial Gallons = 159 L

Gasoline/Petrol

1 x 42 US gallons makes 19.5 US gallons of gas/petrol

Energy density of liquid fuels

  • Gasoline = 34.8 MJ/L = 9.66kWh
  • Ethanol = 23.5 MJ/L  = 6.53kWh
  • Methanol = 17.9 MJ/L = 4.972kWh
  • Diesel = 38.6 MJ/L  =  10.72kWh
  • Aviation Fuel = 33.5 MJ/L = 9.305kWh
  • LPG = 25.3MJ/L = 7.03kWh