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A unit of energy equal to one trillion watt-hours; it measures an amount accumulated over time, rather than power at one moment.
Save conceptA terawatt-hour is a large unit of energy. A watt-hour represents the energy associated with one watt of power sustained for one hour. The prefix tera scales the unit to one trillion watt-hours. Energy suppliers use larger units when the amounts involved would be awkward to describe in individual watt-hours.
Power measures the rate at which energy is delivered or used. Multiplying a constant power level by the time for which it operates gives an energy quantity. A terawatt is therefore a power unit, while a terawatt-hour is an energy unit. The hour is part of the unit, not a statement that the supply must occur within one hour.
Suppose an installation delivers a constant one gigawatt for one thousand hours. Multiplying the power by the duration gives one thousand gigawatt-hours, equal to one terawatt-hour. This assumes the output stays constant throughout. The values are hypothetical and do not describe the Equinor agreement, an actual power station or a current country’s consumption.
A gas contract can state both energy content and cubic metres of gas. The first concerns the energy available; the second concerns physical volume under the specified measurement conditions. Conversion depends on the gas and measurement basis. A terawatt-hour figure alone does not establish a contract’s price, delivery schedule or emissions footprint.
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