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The kilowatt hour (SI symbol kWh, kW⋅h or kW h) is a derived unit of energy equal to 3.6 megajoules.
Calories are units of energy. Various definitions exist but fall into two broad categories. The first, the small calorie, or gram calorie (symbol: cal), is defined as the approximate amount of energy needed to raise the temperature of one gram of water by one degree Celsius at a pressure of one atmosphere.