Electric BillsWhat Is a Kilowatt-Hour (kWh)? How to Calculate Electricity Cost
A kilowatt-hour is 1,000 watts used for one hour. Here's how kWh differs from kW and how to calculate what any appliance costs to run.
kWh calculator: watts to kilowatt-hours
Convert watts and hours of use into kilowatt-hours (kWh) – the unit on your electric bill – and see what that energy costs at your state's rate.
State rates are 12-month residential averages from EIA, through August 2026. Use the rate on your own bill for the most accurate result.
How to use the kwh calculator
- Enter the power in watts (or kilowatts × 1,000).
- Enter hours of use per day and days per month.
- Choose your state to price the energy, or type your own rate.
- Read kWh per day, month and year, and the cost.
Formula
kWh = watts × hours ÷ 1,000. Example: a 1,500-watt heater for 3 hours = 1,500 × 3 ÷ 1,000 = 4.5 kWh. To go back from kWh to average watts: watts = kWh × 1,000 ÷ hours.
Worked examples
| Power | 1 hour | 8 hours | 8 h/day for a month | Monthly cost (US avg) |
|---|---|---|---|---|
| 10 W | 0.010 kWh | 0.08 kWh | 2.4 kWh | $0.44 |
| 60 W | 0.060 kWh | 0.48 kWh | 14.6 kWh | $2.65 |
| 100 W | 0.100 kWh | 0.80 kWh | 24.3 kWh | $4.42 |
| 500 W | 0.500 kWh | 4.00 kWh | 121.7 kWh | $22.10 |
| 1,000 W | 1.000 kWh | 8.00 kWh | 243.4 kWh | $44.19 |
| 1,500 W | 1.500 kWh | 12.00 kWh | 365.0 kWh | $66.29 |
| 2,000 W | 2.000 kWh | 16.00 kWh | 486.7 kWh | $88.39 |
| 5,000 W | 5.000 kWh | 40.00 kWh | 1,216.8 kWh | $220.97 |
What common appliances cost to run
- Space heater (750–1,500 W)
- Refrigerator (725 W)
- Clothes dryer (1,800–5,000 W)
- Washing machine (350–500 W)
- Dishwasher (1,200–2,400 W)
- Electric water heater (4,500–5,500 W)
- Microwave (750–1,100 W)
- Window fan (55–250 W)
- Ceiling fan (65–175 W)
- Furnace fan (750 W)
- Dehumidifier (785 W)
- Coffee maker (900–1,200 W)
- Electric kettle (1,500 W)
- Toaster (800–1,400 W)
- Toaster oven (1,225 W)
- Hair dryer (1,200–1,875 W)
- Clothes iron (1,000–1,800 W)
- Vacuum cleaner (1,000–1,440 W)
- Desktop computer (120 W)
- Laptop (50 W)
- Television (flat screen) (120 W)
- Electric blanket (60–100 W)
- Well pump (250–1,100 W)
- Aquarium (50–1,210 W)
Frequently asked questions
How many kWh is 1,000 watts?
1,000 watts running for one hour uses exactly 1 kWh. Running for 5 hours, it uses 5 kWh.
How do I convert watts to kWh?
Multiply watts by hours of use and divide by 1,000.
How many kWh does a house use per month?
The average US home used about 1,152 kWh in August 2026 (EIA). Usage varies a lot by state and season.
What is the difference between kW and kWh?
kW measures power at a moment; kWh measures energy used over time. A 2 kW appliance running for 3 hours uses 6 kWh.
Related guides
Electric Bills
Electric BillsHow to Read Your Electric Bill: kWh, Supply vs. Delivery, Fixed Charges and Riders
A line-by-line guide to your electric bill: kWh usage, supply and delivery charges, fixed customer charges, riders and taxes, and how to find your real cost per kWh.
Saving EnergyPhantom (Standby) Power: What It Costs and How to Cut It
Standby or phantom power can make up 5–10% of home energy use, per DOE. Learn how to measure it, calculate its cost and cut it.
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