Electricity Cost Calculator: What an Appliance Costs to Run per Hour, Day, Month and Year
Work out what any appliance or device costs to run from its watts (or kW, BTU/h, hp), hours of use and your electricity rate: cost per hour, day, week, month and year, kWh used, standby power and part-load use.
How it works
kWh per day = watts × number of devices × load % × hours per day ÷ 1,000 (+ standby watts × hours off ÷ 1,000) · cost = kWh × rate · month = day × 30.42 · year = day × 365
Your utility bills you for kilowatt-hours (kWh): 1,000 watts running for one hour. Multiply the device’s power by the hours it runs and divide by 1,000 to get kWh, then multiply by your price per kWh. The calculator accepts power in watts, kilowatts, BTU per hour (1 BTU/h = 0.293 W, common on heaters and air conditioners) or horsepower (1 hp = 745.7 W, common on pumps and motors), and time in hours or minutes per day or hours per week. Under More options you can enter several identical devices, use on only some days of the week, an average load for appliances that cycle on and off (a fridge compressor or a heater on a thermostat rarely draws its full rating all the time), and a standby draw for the hours the device is off but still plugged in. A month is taken as an average month, 365 ÷ 12 = 30.42 days, so twelve months add up to exactly one year; the notes also show a 30-day figure for comparison with a bill. Use your all-in rate: divide the total of a recent bill (energy, delivery, taxes and fees) by the kWh on it. The US average residential price was 17.3¢ per kWh in 2025 and the EIA expects about 18.2¢ in 2026, but local rates range from about 11¢ to over 40¢.
Worked example
A 1,500 W space heater running 4 hours a day uses 1,500 × 4 ÷ 1,000 = 6 kWh a day. At 18.2¢ per kWh that is 6 × 0.182 = $1.092 a day, so about $1.09 per day, $7.64 per week, $33.21 per average month (6 kWh × 30.42 days = 182.5 kWh) and $398.58 per year (2,190 kWh). Each hour of use costs $0.273, about 27¢.
Sources: U.S. EIA — Short-Term Energy Outlook: electricity (residential price 17.3¢/kWh in 2025, 18.2¢ forecast for 2026; Oct 2026) · Omni Calculator — Electricity cost calculator (formula and worked example) · Inch Calculator — Electricity cost calculator (worked examples) · Calculator.net — Electricity calculator (unit conversions BTU/h, hp)
Frequently asked questions
How do I calculate the cost of running an appliance?
Multiply its wattage by the hours it runs per day and divide by 1,000 to get kWh per day. Multiply by your price per kWh for the daily cost, then by 30.42 for an average month or by 365 for a year. A 100 W device on for 10 hours uses 1 kWh, which costs 18.2¢ at the 2026 US average rate.
Is the label wattage what the device actually draws?
The label is the maximum. Many devices cycle or idle below it: a fridge rated 150 W runs its compressor only part of the time, and a heater on a thermostat switches off once the room is warm. Set the average load under More options, or use a plug-in watt meter to measure the true average draw.
How much does it cost to run something for one hour?
Divide the watts by 1,000 and multiply by your rate. A 1,500 W heater uses 1.5 kWh in an hour, which costs 1.5 × 18.2¢ = 27.3¢ at the 2026 US average price. The “Cost per hour of use” result shows this for your inputs.
Why is my rate higher than the advertised supply rate?
Bills add delivery charges, taxes and fees on top of the generation rate. Divide your total bill by the kWh used to get your true all-in rate, and enter that number here.
How do I convert BTU or horsepower to watts?
One BTU per hour is 0.293 W, so a 5,000 BTU/h air conditioner’s cooling output equals about 1,465 W of heat moved. Note that an AC’s electrical draw is lower than its BTU rating (divide BTU/h by its EER to get watts). One horsepower is 745.7 W of mechanical output; a motor draws somewhat more because of its efficiency.
Do 240 V appliances work the same way?
Yes. Watts are watts regardless of voltage. A 5,000 W electric dryer on a 240 V circuit still uses 5 kWh for each hour it heats.
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This calculator is for educational purposes. Double-check important results before acting on them.