kW to kWh Calculator
Kilowatts measure power—the rate of energy use. Kilowatt-hours measure energy accumulated over time. Enter both power and hours to calculate kWh and cost.
Quick answerMultiply kilowatts by hours. A constant 2 kW load running for 5 hours uses 10 kWh. At $0.17/kWh, that energy costs $1.70. Kilowatts alone cannot be converted to kWh without a time period.
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Measure representative kW and accumulated kWh safely
Use a plug-in meter only for a compatible 120 V appliance. Hardwired, high-power or panel-level loads require suitable equipment, system checks and qualified installation.
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Amazon opens in a new tab. Confirm the complete voltage, plug, current, startup and installation requirements before ordering. Never improvise a plug adapter or insert a consumer meter into hardwired or unsuitable high-power equipment.
How it works
Energy in kilowatt-hours = average real power in kilowatts × operating time in hours. Cost = kilowatt-hours × electricity rate. For watts, first divide by 1,000: 1,500 W = 1.5 kW. A changing load requires an average power or separate time blocks; multiplying maximum power by all elapsed time gives an upper scenario, not necessarily measured use.
kW to kWh examples at $0.17 per kWh
Each row assumes the stated power stays constant for the complete time. Enter a measured or representative average for cycling equipment.
| Power | Time | Energy | Cost |
|---|---|---|---|
| 0.1 kW | 10 hours | 1.00 kWh | $0.17 |
| 0.5 kW | 8 hours | 4.00 kWh | $0.68 |
| 1 kW | 1 hour | 1.00 kWh | $0.17 |
| 1.5 kW | 4 hours | 6.00 kWh | $1.02 |
| 2 kW | 5 hours | 10.00 kWh | $1.70 |
| 3.5 kW | 8 hours | 28.00 kWh | $4.76 |
| 7.2 kW | 4 hours | 28.80 kWh | $4.90 |
The cost column excludes fixed charges and any taxes or fees not included in the entered per-kWh rate.
Worked example: 2 kW for 5 hours
Energy = 2 kW × 5 h = 10 kWh. At $0.17/kWh, cost = 10 × $0.17 = $1.70. The result covers only that five-hour period. If the same schedule occurs daily, multiply the result by the number of days; if it happens once, do not annualize it.
EIA defines one kilowatt-hour as one kilowatt of power used for one hour. The hour is part of the unit, so adding another division by 60 after entering hours would be incorrect.
Power and energy answer different questions
kW is an instantaneous or average rate. kWh is the total energy accumulated across a period. A 4 kW device used for half an hour and a 1 kW device used for two hours both use 2 kWh.
You cannot convert kW to kWh without time. If a meter or bill already reports kWh, do not multiply it by hours again.
Use average real power for changing loads
Heaters cycle, compressors ramp, chargers taper and variable-speed equipment changes power. For those loads, use average kW over the relevant period, add separate kW × hour blocks, or use accumulated kWh from suitable metering.
A nameplate maximum can support an upper-bound scenario, but it may overstate routine energy. Electrical input and useful output are also different quantities for motors, heat pumps and other conversion equipment.
Match the rate to the same time period
On a flat tariff, one per-kWh rate may be enough. On time-of-use pricing, calculate each rate period separately and add the costs, or use a kWh-weighted average rate. Fixed monthly charges do not change merely because this load uses another kWh, while variable delivery charges may.
For a whole bill, use actual tariff line items and interval data rather than a statewide average price.
Sources used for assumptions: U.S. Energy Information Administration — watts, kilowatts and kilowatt-hours; U.S. Energy Information Administration — electricity glossary definitions; U.S. Department of Energy — utility energy, demand and fixed rate components.
Frequently asked questions
How do I convert kW to kWh?
Multiply average real power in kW by operating time in hours. For example, 2 kW × 3 hours = 6 kWh.
Can I convert kW to kWh without time?
No. kW is a rate and kWh is accumulated energy, so a time period is required.
What is the difference between kW and kWh?
Kilowatts measure power at a moment or averaged over a period. Kilowatt-hours measure the total energy used across that period.
How do I convert watts to kW?
Divide watts by 1,000. For example, 500 W = 0.5 kW and 1,500 W = 1.5 kW.
Should I use maximum or average power?
Use average real power for the period when available. Maximum rating multiplied by all elapsed time is an upper scenario for equipment that cycles or changes power.
How do I handle time-of-use electricity rates?
Calculate kWh and cost separately for each rate period, then add the costs. A weighted average rate is also valid when it is based on the same kWh distribution.
Does this calculate demand charges?
No. It calculates energy cost from kWh. Demand charges use maximum kW under tariff-specific timing and rules.
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