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 kilocalorie (dietary)?
A kilocalorie, written as Calorie with a capital C in nutrition contexts, is a unit of energy equal to 1,000 thermochemical calories. It is the standard unit used to express the energy content of food on nutrition labels globally.
Real-world uses
Kilocalories are the standard unit for food energy labelling in the United States (labelled as "Calories" with a capital C), dietary planning, and exercise energy expenditure. A typical adult needs about 2,000 kcal/day. Fitness trackers report calories burned in kcal.
History
Wilbur Atwater pioneered the use of kilocalories for food energy measurement in the 1890s. The confusing convention of using a capital-C "Calorie" to mean kilocalorie originated in American nutritional science and persists on US food labels today.
Common mistakes
The most common mistake is confusing Calories (kcal) with calories (cal)—they differ by a factor of 1,000. When food labels say "100 Calories," they mean 100 kilocalories. Also, assuming all macronutrients have the same caloric density (fat has 9 kcal/g vs 4 kcal/g for protein and carbohydrates).
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. Nutritional information is labelled in kilocalories in some countries and kilojoules in others, making this conversion important for dietary planning and food science.
Worked examples
1 kilowatt hour = 860.4206501 kilocalorie (dietary)
1 kilocalorie (dietary) = 4,184 joule
How to convert kilowatt hour to kilocalorie (dietary)
To convert kilowatt hour to kilocalorie (dietary), multiply the value by 860.4206501.
To convert kilocalorie (dietary) back to kilowatt hour, multiply by 0.00116222.
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 kilocalorie (dietary)
| kilowatt hour | kilocalorie (dietary) |
|---|---|
| 0.1 | 86.04206501 |
| 0.5 | 430.21032505 |
| 1 | 860.4206501 |
| 2 | 1,720.84130019 |
| 5 | 4,302.10325048 |
| 10 | 8,604.20650096 |
| 25 | 21,510.51625239 |
| 50 | 43,021.03250478 |
| 100 | 86,042.06500956 |
| 250 | 215,105.1625239 |
| 500 | 430,210.3250478 |
| 1,000 | 860,420.6500956 |
Common values
| kilowatt hour | kilocalorie (dietary) | |
|---|---|---|
| A food calorie (1 kcal) | 0.00116222 kilowatt hour | 1 kilocalorie (dietary) |
| A AA battery | 0.0026 kilowatt hour | 2.23709369 kilocalorie (dietary) |
| Boiling a kettle | 0.11666667 kilowatt hour | 100.38240918 kilocalorie (dietary) |
| Daily human diet (2000 kcal) | 2.32444444 kilowatt hour | 2,000 kilocalorie (dietary) |
| 1 gallon of gasoline | 36.6 kilowatt hour | 31,491.3957935 kilocalorie (dietary) |
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.