Northern Ireland's total primary energy consumption is approximately 4.90 million tonnes of oil equivalent.

It is often expressed in tonnes of oil equivalent(toe) or watt-hour(Wh).

Also used is the Mtoe, or Millions of tonnes of oil equivalent, a metric measurement equivalent to approximately 0.006841 BBOE.

Whenever possible the calculation should be in units of energy such as tonnes of oil equivalent (TOE), but if such data is not readily available other units (for example kg.

In the petroleum industry the tonne of oil equivalent (toe) is a unit of energy: the amount of energy released by burning one tonne of crude oil, approximately 42 GJ.

As well as a small population (4. 1 million) and this embarrassment of hydrocarbon reserves (715 tonnes of oil equivalent, for every inhabitant of Norway), Norway also has an abundance of hydro-electric power.

This means, as an example, that if Romania imports around 14 million tonnes of oil equivalent in Russian gas annually, almost one million tonnes of oil equivalent are wasted annually due to defective insulation in blocks of flats.

More recently, the Key World Energy Statistics Report produced by the International Energy Agency stated a figure of 12,267 million tonnes of oil equivalent (Mtoe) of total primary energy supply in the year 2008 having increased from 12,097 Mtoe in the previous year.

Based on an audit of reserves conducted by DeGolyer and MacNaughton and according to the Petroleum Resources Management System standards, the company's proven reserves as at the end of 2011 totaled 1.13 billion tonnes of oil equivalent, and its reserve replacement ratio was over 286%.