What is kilowatt hour?
A kilowatt hour is a unit of energy equal to 1,000 watt hours. It is the standard billing unit used by electricity providers worldwide to measure household and commercial energy consumption.
Real-world uses
The kilowatt-hour is the standard unit for electricity billing worldwide. A typical household uses 250–1,000 kWh per month. EV charging, home appliance energy consumption, and solar panel production are all expressed in kWh. Utility bills list total kWh consumed and price per kWh.
History
The kilowatt-hour became the standard billing unit for electricity in the early 20th century as public electricity grids were established. Its use is mandated for utility metering in most countries. It equals exactly 3,600,000 joules (3.6 MJ).
Common mistakes
Writing "kW/h" instead of "kWh"—the slash implies division (kW per hour), which is a rate of power change, not an energy unit. Also confusing kWh with kW: a 2 kW heater running for 4 hours uses 8 kWh of energy, not 8 kW.
What is calorie (thermochemical)?
The thermochemical calorie is a unit of energy equal to approximately 4.184 joules. It is used in chemistry and physics to express small heat quantities, particularly in thermochemical experiments.
Real-world uses
The thermochemical calorie (4.184 J) is used in chemistry for expressing heats of reaction, specific heat capacities of substances, and calorimetry experiments. It appears in older scientific literature and some chemistry textbooks, particularly in calorimetric calculations.
History
The calorie was first defined by Nicolas Clément in 1824 as the heat needed to raise 1 gram of water by 1°C. The thermochemical calorie (exactly 4.184 J) was later standardized for precise scientific use, distinguishing it from other calorie definitions.
Common mistakes
Confusing the small calorie (cal, 4.184 J) with the large Calorie/kilocalorie (Cal/kcal, 4,184 J) used in food labelling. Also, several slightly different definitions of the calorie exist (thermochemical, 15°C, IT), which differ by fractions of a percent.
When is this conversion used?
Electricity bills use kilowatt-hours while physics calculations use joules. Converting between them is essential for energy audits, comparing appliance efficiency, and understanding power consumption.
Worked examples
1 kilowatt hour = 860,420.6500956 calorie (thermochemical)
1 calorie (thermochemical) = 4.184 joule
How to convert kilowatt hour to calorie (thermochemical)
To convert kilowatt hour to calorie (thermochemical), multiply the value by 860,420.6500956.
To convert calorie (thermochemical) back to kilowatt hour, multiply by 0.00000116.
Measurement standards
The joule is the SI derived unit of energy, defined as one kilogram-metre-squared per second-squared (kg·m²/s²). The kilowatt-hour, equal to exactly 3.6 megajoules, is accepted for use with the SI by the BIPM for practical electricity metering.
Did you know?
A single bolt of lightning releases roughly 1 to 5 gigajoules of energy, yet only a small fraction reaches the ground as electrical current. Most of the energy dissipates as light, heat, and the thunder shockwave.
Quick reference: kilowatt hour to calorie (thermochemical)
| kilowatt hour | calorie (thermochemical) |
|---|---|
| 0.1 | 86,042.06500956 |
| 0.5 | 430,210.3250478 |
| 1 | 860,420.6500956 |
| 2 | 1,720,841.3001912 |
| 5 | 4,302,103.25047801 |
| 10 | 8,604,206.50095602 |
| 25 | 21,510,516.25239006 |
| 50 | 43,021,032.50478011 |
| 100 | 86,042,065.00956023 |
| 250 | 215,105,162.52390057 |
| 500 | 430,210,325.04780114 |
| 1,000 | 860,420,650.09560227 |
Common values
| kilowatt hour | calorie (thermochemical) | |
|---|---|---|
| A food calorie (1 kcal) | 0.00116222 kilowatt hour | 1,000 calorie (thermochemical) |
| A AA battery | 0.0026 kilowatt hour | 2,237.09369025 calorie (thermochemical) |
| Boiling a kettle | 0.11666667 kilowatt hour | 100,382.40917782 calorie (thermochemical) |
| Daily human diet (2000 kcal) | 2.32444444 kilowatt hour | 2,000,000 calorie (thermochemical) |
| 1 gallon of gasoline | 36.6 kilowatt hour | 31,491,395.79349904 calorie (thermochemical) |
Available Energy units
More kilowatt hour conversions
- Convert kilowatt hour to joule
- Convert kilowatt hour to kilojoule
- Convert kilowatt hour to calorie (thermochemical)
- Convert kilowatt hour to kilocalorie (dietary)
- Convert kilowatt hour to watt hour
- Convert kilowatt hour to megajoule
- Convert kilowatt hour to electronvolt
- Convert kilowatt hour to British thermal unit
- Convert kilowatt hour to therm (US)
Assumption: calorie means thermochemical calorie, and therm means US therm.