kilowatt hour (kWh)
Standard unit for electricity billing.
The kilowatt-hour (kWh) is a unit of energy equal to 3.6 megajoules. It is commonly used as a billing unit for energy delivered to consumers by electric utilities.
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Here you can convert units like terawatt hour, gigawatt hour, megawatt hour, kilowatt hour, etc. within the energy category.
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All units in energy
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terawatt hour
TWh
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gigawatt hour
GWh
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megawatt hour
MWh
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megajoule
MJ
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kilojoule
kJ
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watt second
Ws
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quad
quad
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therm
therm
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foot-pound
ft×lb
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Common mistakes in energy conversion
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Kilowatts (kW) and kilowatt-hours (kWh) are constantly confused: kW is power, how fast energy is being used right now, while kWh is an amount of energy, power times time. A 2 kW heater running for 3 hours uses 2 × 3 = 6 kWh. Your electricity bill counts kWh; your main fuse limits kW.
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Food 'calories' are actually kilocalories: 1 kcal = 1,000 cal. A '500-calorie' meal therefore contains 500 kcal, half a million small calories. Labels write the same thing as 'kcal' or as 'Cal' with a capital C.
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The relationship is exact: 1 kWh = 3.6 MJ (3,600 kJ, because an hour has 3,600 seconds). The common slip is dividing when you should multiply: 10 kWh is 36 MJ, not 2.8. Remember the direction: kWh → MJ means times 3.6.
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The 'BTU' rating on AC units and heat pumps almost always means BTU per hour, a power, not an amount of energy. A '12,000 BTU' unit delivers about 3.5 kW of cooling continuously, not a fixed energy budget. Compare via 1 kW ≈ 3,412 BTU/h.
Quick conversion quiz
Score:
0
2 kilowatt hour equals 7.2e+3 kilojoule.
Correct answer: 2 kilowatt hour = 7.2e+3 kilojoule.
50 kilowatt hour equals 9.0e+5 kilojoule.
Correct answer: 50 kilowatt hour = 1.8e+5 kilojoule.
24.7 megajoule equals 6.17 kilowatt hour.
Correct answer: 24.7 megajoule = 6.86 kilowatt hour.
25 kilowatt hour equals 9.0e+4 kilojoule.
Correct answer: 25 kilowatt hour = 9.0e+4 kilojoule.
Definitions
joule (J)
The SI derived unit of energy.
The joule (J) is the SI unit of energy. It is defined as the work done by a force of one newton acting through one meter. It is also the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second.
electronvolt (eV)
Tiny unit of energy used in particle physics.
The electronvolt (eV) is a unit of energy equal to approximately 1.6×10^-19 joules. It is the amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt.
british thermal unit (BTU)
Unit for heat energy (HVAC).
The British thermal unit (BTU) is a unit of heat; it is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. It is commonly used in heating and air conditioning (HVAC).
kilocalorie (kcal)
Common unit for food energy.
The kilocalorie (kcal), often simply called 'calorie' in nutrition, is a unit of energy. It was originally defined as the heat required to raise the temperature of 1 kg of water by 1 °C. In nutrition labels, 1 Calorie (capital C) usually means 1 kilocalorie.
calorie (cal)
Small calorie (gram calorie).
The calorie (cal) is a pre-SI metric unit of energy. It is defined as the amount of heat needed to raise the temperature of one gram of water by one degree Celsius. It is 1/1000 of a kilocalorie.
Frequently asked questions
What is the difference between kW and kWh?
kW is power (the rate of energy use). kWh is energy used over time (power × hours). Example: 2 kW for 3 hours = 6 kWh.
How many joules are in 1 kWh?
1 kWh equals 3,600,000 joules (3.6 MJ).
What is the difference between joules (J) and watt‑hours (Wh)?
Both measure energy. 1 Wh equals 3600 joules. Joules are SI units; Wh is common for electricity.
What is the difference between a calorie and a Calorie?
A calorie (cal) is small. A food Calorie (Cal) is a kilocalorie: 1 Cal = 1 kcal = 1000 cal.
How many joules are in a calorie?
1 cal is about 4.184 joules. 1 kcal (food Calorie) is about 4184 joules.
Why is electricity billed in kWh instead of watts?
Watts measure instant power. Billing is based on total energy over time, which is measured in kWh.
How do I use the energy converter on konvertera.nu?
Enter your energy value (like kWh), choose the target unit (like J or MJ), and the converter will show the converted result.