The tonne of oil equivalent
) is a unit of energy
: the amount of energy released by burning one tonne
of crude oil
, approximately 42 GJ
(as different crude oils have different calorific values
, the exact value of the toe
is defined by convention; unfortunately there are several slightly different definitions as discussed below).
The toe is sometimes used for large amounts of energy, as it can be more intuitive to visualise, say, the energy released by burning 1000 tonnes of oil than 42,000 billion joules (the SI unit of energy).
Multiples of the toe are used, in particular the megatoe (Mtoe, one million toe) and the gigatoe (Gtoe, one billion toe).
The IEA/OECD define one toe to be equal to 41.868 GJ or 11.630 MWh.
Some organisations use other definitions of toe, for example:
- 1 toe = 42 GJ
- 1 toe = 41.85 GJ
- 1 toe = 7.11, 7.33, or 7.4 barrel of oil equivalent (boe)
- 1 tonne petroleum equivalent (TPE), as used in renewable energy, 45.217 GJ.
- 1 barrel of oil equivalent (boe) contains approximately 0.146 toe (i.e. there are approximately 6.841 boe in a toe).
- 1 t diesel = 1.01 toe
- 1 m3 diesel = 0.98 toe
- 1 t petrol = 1.05 toe
- 1 m3 petrol = 0.86 toe
- 1 t biodiesel = 0.86 toe
- 1 m3 biodiesel = 0.78 toe
- 1 t bioethanol = 0.64 toe
- 1m3 bioethanol = 0.51 toe
- 1 MWh = 0.22 toe (assumes 39% thermal to electrical conversion efficiency)
It is important to note that toe should be used carefully when converting electrical units - for instance, BP's 2007 report used a factor of 38% efficiency (the average efficiency of OECD thermal generating units in 2006), or roughly 16 GJ per toe, when converting kilowatt-hours to toe.