Electricity Cost Calculator
Cost = watts × hours × days ÷ 1,000 × price per kWh: a 1,500 W space heater run 8 h a day for 30 days uses 360 kWh, so $65.92 at the U.S. average of 18.31¢ (EIA, July 2026). At the Massachusetts average, 30.49¢ (EIA, July 2026), the same heater costs $109.76: pick your state or your own rate.
Cost per month
$65.92
360 kWh a month
- Per year (12 months)
- $790.99, 4,320 kWh
- Per day of use
- $2.20, 12 kWh
- Price used
- 18.31¢/kWh, U.S. average, EIA July 2026
The EIA price is utility revenue ÷ kWh sold, service charges spread in: it is not your utility's rate per kWh.
Checked by the Yardstick Math team · How we check
Worked examples
A 1,500 W space heater, 8 hours a day for 30 days (EIA prices, July 2026)
- 1,500 × 8 × 30 ÷ 1,000 = 360 kWh
- 360 × 18.31 ÷ 100 = $65.92 at the U.S. average
- 360 × 30.49 ÷ 100 = $109.76 in Massachusetts
Result: 360 kWh: $65.92 a month (U.S. average), $109.76 in Massachusetts.
Checked by the automated test “electricity-cost — space heater 1,500 W, 8 h a day, 30 days → 360 kWh, $65.92 at 18.31¢ (U.S.), $109.76 at 30.49¢ (MA)”.
The average U.S. home for a year (EIA price, July 2026)
- EIA: 10,791 kWh a year, about 899 kWh a month
- 10,791 × 18.31 ÷ 100 = $1,976
Result: About $1,976 a year at the U.S. average price.
Checked by the automated test “electricity-cost — EIA average home 10,791 kWh a year × 18.31¢ → $1,976 a year”.
How it works
kWh = watts × hours per day × days ÷ 1,000
Cost = kWh × price in cents per kWh ÷ 100
Cost per year = cost per month × 12
Assumptions
- Watts and kWh are the same units everywhere: there is no metric version to convert.
- The state prices are EIA's average residential price for the latest month published (July 2026): utility revenue ÷ kWh sold, service charges and surcharges included. It is not your utility's rate.
- The appliance draws its full power for every hour typed: a thermostat or a compressor that cycles uses less.
- Results are rounded for display only; the calculation keeps full precision.
Reference table
| Appliance | U.S. 18.31¢ | Mass. 30.49¢ | Texas 15.88¢ |
|---|---|---|---|
| Space heater 1,500 W, 8 h a day | $65.92 | $109.76 | $57.17 |
| Window air conditioner 1,000 W, 8 h a day | $43.94 | $73.18 | $38.11 |
| Desktop computer 200 W, 8 h a day | $8.79 | $14.64 | $7.62 |
| TV 100 W, 5 h a day | $2.75 | $4.57 | $2.38 |
| LED bulb 10 W, 5 h a day | $0.27 | $0.46 | $0.24 |
An appliance on a thermostat runs fewer hours than it is switched on: type the hours it really runs.
Before you start
- Find the watts. They are printed on the label or in the manual; 1 kW = 1,000 W (EIA).
- Count the hours it runs. Hours per day, then days per month: a heater used on weekends only runs 8 or 9 days a month.
- Choose a price. Your state’s EIA average, or your bill total ÷ the kWh on it.
Common mistakes
- Mixing up watts and kWh Watts measure power at one moment, kWh measure energy over time (EIA). A 1,500 W heater on for one hour uses 1.5 kWh, not 1,500: $0.27 at the U.S. average of 18.31¢ (EIA, July 2026).
- Using the label's watts for every hour on a thermostat The calculator counts full power for every hour typed. A heater on a thermostat, a fridge or an air conditioner switches itself on and off: type the hours it actually runs, not the hours it is plugged in.
- Using the U.S. average in an expensive state Hawaii averaged 48.00¢ per kWh in July 2026 against 18.31¢ for the U.S. (EIA): the same 360 kWh heater month costs $172.80 there, not $65.92.
- Reading the EIA average as your rate EIA divides utility revenue by kWh sold; that revenue includes service charges, surcharges and taxes paid by the utility, and EIA says it “does not reflect the per kWh rate” each customer pays. Divide your bill total by its kWh and choose “My own rate”.
Frequently asked questions
How do you calculate kWh?
Watts × hours ÷ 1,000. EIA's example: a 40 W bulb on for 5 hours uses 200 Wh, or 0.2 kWh: $0.04 at 18.31¢ (EIA, July 2026). A 1,500 W heater run 8 hours a day for 30 days uses 360 kWh.
How much is a kWh?
The U.S. residential average was 18.31¢ in July 2026 (EIA), from 12.72¢ in Louisiana to 48.00¢ in Hawaii. Your own price is your bill total ÷ the kWh on it.
How much does it cost to run a space heater?
A 1,500 W heater uses 1.5 kWh an hour: $0.27 an hour at the U.S. average of 18.31¢ (EIA, July 2026), $65.92 for 8 hours a day over 30 days. On its thermostat it runs fewer hours and costs less.
How do you calculate electricity cost?
kWh × price per kWh. The average U.S. home bought 10,791 kWh a year (EIA, 2022 data); at 18.31¢ (EIA, July 2026) that is about $1,976 a year.
Sources
Formula, examples and sources checked on by the Yardstick Math team. How we check our formulas.
- Electric Power Monthly, Table 5.6.A: Average Price of Electricity to Ultimate Customers by End-Use Sector, by State — U.S. Energy Information Administration, accessed
- Electric Power Monthly, Technical Notes — U.S. Energy Information Administration, accessed
- Electricity explained: Measuring electricity — U.S. Energy Information Administration, accessed
- How much electricity does an American home use? (FAQ) — U.S. Energy Information Administration, accessed