# 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