kilojoule per kilowatt-hour

One kilojoule of fuel heat for each kilowatt-hour of electricity sent out. A kilowatt-hour is exactly 3,600 kilojoules, so a plant that turned all of its fuel heat into electricity would have a heat rate of exactly 3,600 kJ/kWh, and every real plant is higher. The conversion is exact.

Watch out: A lower heat rate is better, which is the opposite of an efficiency. It also depends on which heating value of the fuel was used: the higher heating value counts the heat of the water vapour the fuel makes, the lower heating value does not, and the two differ by about 10 % for natural gas. A heat rate with no statement of which was used is ambiguous.

Heat rate is the power industry's inverse of efficiency, and it survives because the numbers are easy to compare: a modern combined-cycle gas plant runs near 7,000 to 8,000 kJ/kWh and an older coal plant near 10,500 to 11,500. It is quoted in kilojoules per kilowatt-hour in most of the world outside North America.

One kilojoule per kilowatt-hour in every heat rate unit

• Power Plant Heat Rate

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