2.1.2 Energy use and energy units

Course subject(s) 2. Accounting energy use and GHG emissions

The video you are about to see will be about energy use and energy units

Key takeaways:

  • The unit of energy is the Joule, J
  • Power is equal to energy per unit time, it has the unit Watt, W
  • The kilowatt hour is another unit of energy. 1 kWh is equal to 3.6 MJ
  • There are numerous other units of energy which can all be expressed in an equivalent number of Joules.

Summary of some important data and equations:

Overview of units of energy use and their conversion to the SI-unit joule.
Unit Conversion to joules (multiply by…) Remarks
calorie (cal) 4.1868 Old unit for quantiles of heat
tonne of oil equivalent (toe) 41.868 x 109 Defined as 107 kcal. The toe is widely used in international energy statistics
barrel of oil equivalent (boe) approx. 6.1 x 109 Conversion values ranging from 6.06 to 6.12 x 109
tonne of coal equivalent (tce) 28.6 x 109 Used as the main unit of energy in China
kilowatt-hour (kWh) 3.6 x 106 Used mainly for electricity
British-thermal-unit (BTU) 1.055 x 103 Used in the USA; other units include the therm (105 BTU) and the quad (1015 BTU)
watt-year (Wyr) 31.5 x 106 Useful unit for analytical applications; if one uses 1 W on average, one uses 1 Wyr in a year


Energy content for a number of energy carriers. For fuels, the energy content is given on the basis of the lower heating value.
Energy content (MJ/kg unless indicated otherwise)
Hard coal (coking coal and bituminous coal) 23 – 30
Brown coal (sub-bituminous coal and lignite) 5 – 17
Crude oil 42 – 44
LPG, Ethane 46 – 47
Gasoline/petrol 44.8 (33 MJ/litre)
Aviation turbine fuel 43.9
Diesel fuel (Gas/diesel oil) 43.4 (36 MJ/litre)
Heavy fuel oil (low sulphur) 40.2
Natural gas 31 – 36 MJ/m3
Wood pellets 17
Methanol 19.9 (15.7 MJ/litre)
Ethanol 26.8 (21.2 MJ/litre)
Electricity 3.6 MJ/kWh
Hot water 90℃ (reference to 10℃) 0.34
Steam, depending on pressure and temperature 2.7 – 3.5
Steam, for heating applications 1.9 – 2.2
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