Watts to kWh calculator
A kilowatt-hour (kWh) is 1,000 watt-hours: a 1,000-watt appliance running for one hour uses 1 kWh, and so does a 100-watt appliance running for 10 hours. Watts are how fast something uses electricity; kWh are how much it used, and kWh is what your utility bills you for.
kWh = watts × hours ÷ 1,000
Cost = kWh × price per kWh (U.S. average 2025: 17.2¢)
How many watts are in a kWh?
None, strictly speaking, because they measure different things: a watt is a rate, a kWh an amount. The useful answer is 1 kWh = 1,000 watts for one hour. One kilowatt (kW) is 1,000 watts. If an appliance draws 250 watts, it takes 4 hours to use 1 kWh.
| Example | Watts | Hours for 1 kWh | kWh in 1 hour | Cost per hour at 17.2¢ |
|---|---|---|---|---|
| LED bulb | 10 | 100.0 | 0.01 | $0.002 |
| Laptop | 60 | 16.7 | 0.06 | $0.010 |
| TV (55-inch, on) | 100 | 10.0 | 0.10 | $0.017 |
| Dehumidifier | 500 | 2.0 | 0.50 | $0.086 |
| Microwave | 1,000 | 1.00 | 1.0 | $0.172 |
| Space heater | 1,500 | 0.67 | 1.5 | $0.258 |
| Electric dryer | 3,000 | 0.33 | 3.0 | $0.517 |
| Electric water heater element | 4,500 | 0.22 | 4.5 | $0.775 |
| Level 2 EV charger | 7,200 | 0.14 | 7.2 | $1.241 |
Example wattages are typical label values; check your own appliance. Many appliances (refrigerators, dehumidifiers, heaters with a thermostat) do not run at full wattage all the time, so the label overstates their use. Average yearly use from the EIA survey: appliance energy use.
kW vs kWh
kW is power at a moment (a car's engine, a solar array's size, a charger's speed); kWh is energy over time (a battery's size, your monthly use). A 7.2 kW charger running for 2 hours delivers 14.4 kWh. The average U.S. home used 874 kWh a month in 2025, which is an average draw of about 1,198 watts around the clock (by state).
Other conversions
| From | To | Formula |
|---|---|---|
| Watt-hours (Wh) | kWh | ÷ 1,000 |
| kWh | Megawatt-hours (MWh) | ÷ 1,000 |
| Amps (A) | Watts | × volts (120 V outlet, 240 V for dryers, ranges, EV chargers) |
| kWh | BTU | × 3,412 |
| Therms (natural gas) | kWh | × 29.3 (1 therm = 100,000 BTU) |
| Horsepower | Watts | × 746 |
Comparing electric and gas heating needs more than a unit conversion, because furnaces lose heat up the flue and heat pumps deliver several kWh of heat per kWh of electricity; the heat pump vs furnace calculator does that for your climate and fuel prices.
Electric bill calculator · Appliance energy use · EV charging cost