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Everyday & Lifestyle
Electricity Cost Calculator — Cost to Run an Appliance by Watts & kWh
Turn an appliance's wattage and your kWh rate into a real dollar cost per day, month and year
Every appliance in your home has a price tag you never see at checkout — the electricity it burns while it runs. This electricity cost calculator turns three numbers you can find in minutes — the device's wattage, how many hours a day it runs, and your rate in cents per kWh — into a clear dollar cost per day, per month and per year. It's the fastest way to answer the question everyone Googles: how much does it cost to run a space heater / air conditioner / refrigerator / hot tub?
The math is simple and exact. Power is measured in watts (W); energy is measured in kilowatt-hours (kWh), which is what your utility actually bills. One kilowatt-hour is 1,000 watts running for one hour. So the formula is:
Cost = (watts ÷ 1,000) × hours used × rate per kWh.
Take a 1,500 W space heater running 3 hours a day at the U.S. average rate of about $0.16/kWh: 1.5 kW × 3 h × $0.16 = $0.72 a day, which is roughly $21.60 a month and $262 a year for that one heater. Swap in your own numbers and the picture changes fast — a 50 W LED TV left on all evening costs pennies, while a 4,000 W central AC unit or an electric water heater can quietly run into hundreds of dollars a year.
Where to find the numbers. Wattage is usually printed on a label on the appliance, in the manual, or on the nameplate near the power cord (sometimes you'll see volts and amps instead — multiply them: 120 V × 5 A = 600 W). Your rate is on your electric bill: take the total dollars charged for energy and divide by the kWh used, or look for the "price per kWh" line. The U.S. residential average is around 16 cents/kWh in 2026, but it ranges from roughly 11¢ in low-cost states to 30¢+ in California, Hawaii and the Northeast — so always plug in your rate for an accurate answer.
Use this tool to compare two appliances before you buy, decide whether it's worth replacing an old energy hog, size up the cost of leaving something on overnight, or sanity-check a surprising electric bill. Results are an estimate for planning — your actual bill also includes delivery charges, taxes and fees that vary by utility, and appliances with thermostats (heaters, AC, fridges) cycle on and off rather than drawing full watts every minute.
📖 See also: How to Calculate a Tip (and Split the Bill)
Calculator
Fill in the fields and click "Calculate" for instant results.
📰 Formula
• Energy per day (kWh) = (watts ÷ 1,000) × hours used per day • Cost per day = energy per day (kWh) × rate per kWh • Cost per month = cost per day × 30.42 (average days per month) • Cost per year = cost per day × 365 • If you only know volts and amps: watts = volts × amps
📰 Formula
• Energy per day (kWh) = (watts ÷ 1,000) × hours used per day • Cost per day = energy per day (kWh) × rate per kWh • Cost per month = cost per day × 30.42 (average days per month) • Cost per year = cost per day × 365 • If you only know volts and amps: watts = volts × amps
🧪 Worked examples
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Example 3
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Example 4
⚠️ Common mistakes
- Entering kilowatts in the watts box (a 1.5 kW heater is 1,500 W, not 1.5).
- Using the appliance's surge/peak wattage instead of its normal running wattage.
- Forgetting that thermostats cycle — a 1,500 W heater set to a comfortable temp may only run part of each hour.
- Using the national average rate instead of your own — rates range from ~11¢ to 30¢+ per kWh.
- Mixing up cents and dollars: 16 cents/kWh is $0.16, not $16.
💡 Tips
- Find your real rate by dividing the energy charge on your bill by the kWh used that month.
- Only have volts and amps? Multiply them: 120 V × 12.5 A = 1,500 W.
- For appliances that cycle (fridge, AC, heater), use a realistic 'hours actually running' number, not 24.
- A kill-a-watt style plug meter gives you exact kWh for a device over a week — divide its cost by 7 for a daily figure.
- To cut the bill, target high-wattage devices that run for long hours — those drive the cost, not the phone charger.
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❓ Frequently asked questions
How do I calculate the cost to run an appliance?
Cost per day = (watts ÷ 1,000) × hours used per day × your rate per kWh. A 1,500 W heater for 3 hours at $0.16/kWh = 1.5 × 3 × 0.16 = $0.72 a day.
What is a kilowatt-hour (kWh)?
A kilowatt-hour is the energy used by a 1,000-watt device running for one hour. It's the unit your electric utility bills you for. A 100 W bulb on for 10 hours uses 1 kWh.
How much does it cost to run a 1,500 watt space heater?
At the U.S. average $0.16/kWh, a 1,500 W heater costs about $0.24 per hour, $0.72 for 3 hours a day, roughly $21.60 a month, or ~$263 a year. Running it 24/7 would be about $5.76 a day.
What is the average cost of electricity per kWh in the US?
The U.S. residential average is around 16 cents per kWh in 2026, but it ranges from about 11¢ in the cheapest states to over 30¢ in Hawaii, California and parts of the Northeast. Use the rate on your own bill for accuracy.
How do I find the wattage of an appliance?
Check the label or nameplate near the power cord, the manual, or the spec sheet. If it only lists volts and amps, multiply them: 120 volts × 5 amps = 600 watts.
How do I find my electricity rate per kWh?
Look on your electric bill for a 'price per kWh' line, or divide the total energy charge by the kilowatt-hours you used that month. Add delivery fees if you want the all-in rate.
How much does it cost to leave a light on all night?
A 60 W incandescent bulb left on 8 hours uses 0.48 kWh — about 8 cents at $0.16/kWh. A 9 W LED for the same time costs about a penny. The wattage is what matters.
Why is my electricity bill higher than this estimate?
Your bill also includes delivery charges, taxes and fees on top of the energy rate, and it covers every device in the home. This calculator estimates one appliance at the energy rate you enter — a planning figure, not the final bill.
How do I convert watts to cost per hour?
Cost per hour = (watts ÷ 1,000) × rate per kWh. A 2,000 W appliance at $0.16/kWh costs 2 × 0.16 = $0.32 per hour to run.