Calories to Kilowatt-hours (cal to kWh)

1 calorie equals 0.000001162222222 kilowatt-hours (rounded).

1 calorie = 0.000001162222222 kilowatt-hours

How to convert calories to kilowatt-hours

To convert calories to kilowatt-hours, multiply the number of calories by 0.000001162222222. The factor is rounded to 10 significant digits. To go the other way, multiply kilowatt-hours by 860,420.6501 (rounded).

kilowatt-hours = calories × 0.000001162222222

Example: 10 calories = 0.00001162222222 kilowatt-hours.

The 'calorie' on food labels is really a kilocalorie. The thermochemical calorie (4.184 J) is used here unless marked IT.

About these units

Calorie (cal)

ScientificTraditional unit (still used in some regions)

The thermochemical calorie: exactly 4.184 joules, the energy to raise one gram of water by one degree Celsius. Not the same as the food Calorie, which is a kilocalorie.

Latin calor, meaning heat, supplied the name. Nicolas Clement used it in lectures on heat engines between 1819 and 1824, and by 1852 Pierre Favre and Jean Silbermann applied it to the small unit based on a single gram of water warmed by one degree Celsius. Because the specific heat of water varies slightly with temperature, early calories differed from one laboratory to the next. A mean value near 4.1855 J was published for the 15 degree calorie in 1950, with an uncertainty of 0.0005 J.

Chemists settled the matter by definition. The thermochemical calorie is exactly 4.184 J, which is the figure used here, and NIST lists it with that exact value. The calorie is not an SI unit and is regarded as obsolete, since the ninth General Conference on Weights and Measures in 1948 preferred the joule for heat. One thousand of these calories make a kilocalorie, the larger unit used for food, and a slightly larger calorie, the International Table version of 4.1868 J, is used in steam tables.

1 calorie = 4.184 joules (exactly).

Sources: Wikipedia: Calorie; NIST SP 811, Appendix B.8 (energy conversion factors)

Kilowatt-hour (kWh)

Metric (SI)Current unit

3.6 million joules, the energy used by a 1,000-watt appliance in an hour. The billing unit for household electricity.

Before it was a line on every power bill, the kilowatt-hour had a British nickname: the Board of Trade unit, abbreviated B.T.U. after the government body that regulated the electricity industry until 1942, when the Ministry of Power took over. In India it is still often called simply a unit, and a million of them, written MU, is a gigawatt-hour.

A kilowatt-hour is the energy of a 1 kW device running for an hour, which is 3.6 MJ, or about 3,412 British thermal units. A 100 W television watched for 10 hours uses one, and boiling a liter of water in an electric kettle takes about 0.1. In 2020 the average US household used 893 kWh a month, an average continuous draw of about 1.22 kW.

Utilities multiply the kilowatt-hours consumed by a price per kWh, and larger customers may also pay for peak demand. One common error is writing kW/h, which would mean kilowatts per hour, a rate of change of power, not energy.

1 kilowatt-hour = 3,600,000 joules (exactly).

Sources: Wikipedia: Kilowatt-hour; Wikipedia: British thermal unit; Wikipedia: Watt-hour

Related conversions

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