UtilibyWritten by the Utiliby editorial team · Last updated October 17, 2026 · Rules and formulas reviewed October 2026
What this free electricity cost calculator does
Few people know what their kettle, heater, gaming PC or air conditioner really costs to run. An electricity cost calculator turns a power rating into pounds, dollars or euros. This free online tool works out the cost of any appliance per hour, day, week, month and year from its wattage, how long you use it and your price per kWh. It also estimates the energy in kWh and the carbon dioxide emitted.
A picker of typical appliances fills in common wattages, and a running-share setting handles items that cycle, such as fridges and water heaters. A whole-home tab adds up to eight appliances and shows which ones cost the most with a share chart, and an upgrade tab shows how long a more efficient bulb or appliance takes to pay for itself. A cumulative cost chart shows the money building up over twelve months. Everything runs in your browser.
How to use the electricity cost calculator
- Enter your price per kWh from your electricity bill.
- Pick a typical appliance or type the watts from the label.
- Set the hours used per day and days per week.
- Adjust the running share for appliances that cycle on and off.
- Read the cost per hour, day, month and year.
- Use the other tabs to total your whole home or test an upgrade.
The electricity cost formula
Cost equals watts divided by 1,000, times hours used, times the price per kWh. A 1,500 W space heater used for 4 hours a day uses 1.5 x 4 = 6 kWh a day. At $0.17 per kWh that is $1.02 a day, about $31.03 a month and $372.30 a year, for 2,190 kWh. If a label gives amps and volts instead of watts, multiply them: 10 amps at 120 volts is 1,200 watts.
| Appliance | Watts | Hours a day | Per month at $0.17 |
|---|---|---|---|
| LED bulb | 9 | 5 | $0.23 |
| Laptop | 50 | 6 | $1.55 |
| TV | 100 | 4 | $2.07 |
| Space heater | 1,500 | 4 | $31.03 |
| Router (always on) | 10 | 24 | $1.24 |
Appliances that cycle on and off
Rated watts are the power an appliance draws while running, but many do not run continuously. A refrigerator might be rated at 150 W yet run only 40 percent of the time, so it averages 60 W and uses about 526 kWh a year, costing around $89 at $0.17. Electric water heaters, air conditioners and heaters with thermostats behave the same way. Set the running-share percentage to reflect this, or use a plug-in energy monitor to measure real use.
Standby power and always-on devices
Devices that never fully switch off add up. A 10 W router, set-top box or charger left plugged in uses 87.6 kWh a year, about $14.89 at $0.17 per kWh. A dozen such loads can cost over $100 a year. Use smart power strips, switch off at the wall and unplug chargers that are not in use. The whole-home tab helps you see how much of your bill is background load.
Do efficient upgrades pay for themselves?
Swapping a 60 W incandescent bulb for a 9 W LED saves 51 W. Used 3 hours a day, that is 55.8 kWh a year, or about $9.49 at $0.17 per kWh. A $2.50 LED bulb pays back in about 96 days and keeps saving for years. The upgrade tab does the same sum for any pair of appliances, adding the cost of the new item, the years you want to count and the carbon saved. Bigger purchases such as fridges and heat pumps have longer paybacks, so check the numbers.
Understanding your electricity rate
Your bill may include a fixed daily charge, a per-kWh energy charge, delivery fees and taxes. For appliance costs, the marginal rate per kWh is what matters. Some tariffs have tiers where the price rises as you use more, and others vary by hour. If your rate varies, enter the one that applies when the appliance runs, or run the calculator twice for peak and off-peak.
Ways to cut your electricity bill
- Switch to LED lighting.
- Use heating and cooling efficiently, with sensible thermostat settings and good insulation.
- Run big appliances off-peak if you have time-of-use rates.
- Unplug or switch off standby devices.
- Choose efficient models when replacing appliances.
- Measure with a plug-in meter to find hidden loads.
Accuracy, privacy and responsible use
The calculator multiplies the figures you enter. Typical wattages are approximations from common appliance ranges, and real devices vary by model, age and setting. Your bill will include other charges. The CO2 factor is an adjustable average, not a measurement for your grid. Nothing you enter leaves your browser.
Related free tools
Use these free online tools together with this one:
- Total up the recurring bills you pay with the subscription cost calculator.
- Fit utility bills into your monthly plan with the budget planner calculator.
- Compare driving costs, including EVs, with the gas trip cost calculator.
- Plan another home cost with the lawn fertilizer calculator.
- Add the cost of cooking energy with the recipe cost calculator.
Frequently asked questions
How do I calculate the cost of running an appliance?
Divide the watts by 1,000 to get kilowatts, multiply by the hours used, then multiply by your price per kWh. A 1,500 W heater for 4 hours at $0.17 per kWh uses 6 kWh and costs $1.02.
What is a kWh?
A kilowatt-hour is the energy used by a 1,000 watt appliance running for one hour. It is the unit your electricity bill is based on.
Where do I find my price per kWh?
Look at your electricity bill or tariff. Use the energy rate per kWh, and if you have tiered or time-of-use rates, use the rate that applies when you use the appliance.
How do I find an appliance's wattage?
Check the label or rating plate on the appliance or the manual. If it only shows amps and volts, multiply them: 10 amps at 120 volts is 1,200 watts. Typical values can be picked from the list.
Why does a fridge use less than its rated watts?
A fridge compressor cycles on and off, running maybe 30 to 40 percent of the time. Use the running-share box to reflect that.
How much does it cost to run a space heater?
A 1,500 W heater costs about $0.26 an hour at $0.17 per kWh. Running 4 hours a day it costs about $31 a month.
How much does an air conditioner cost to run?
It depends on size and efficiency. A 1,000 W window unit running 8 hours a day at $0.17 costs about $1.36 a day. Enter your own watts and hours for your unit.
How much does leaving devices on standby cost?
A 10 W device left on all year uses 87.6 kWh, which costs about $14.89 at $0.17 per kWh. Many small standby loads add up.
How do I calculate monthly electricity cost?
Calculate the cost per year and divide by 12. The tool shows cost per hour, day, week, month and year.
How can I list all my appliances?
Use the whole-home tab. Add up to eight items with watts, hours per day, quantity and running share to see monthly and yearly totals and each item's share of the bill.
How do I work out whether a new appliance will pay for itself?
Use the upgrade payback tab. Enter old and new watts, hours of use and the price. It shows yearly saving and the payback time.
What is the carbon footprint of my electricity use?
Multiply kWh by the emissions factor of your grid. The factor varies by country and region and by time, so the default 0.4 kg per kWh is an editable round number.
Does this include fixed charges and taxes?
No. It uses only the energy rate you enter. Add any per-kWh taxes or surcharges to the rate for a closer figure.
How do I convert watts to kilowatts?
Divide by 1,000. 1,500 watts is 1.5 kilowatts.
Is it cheaper to run appliances at night?
Only if you are on a time-of-use or off-peak tariff. Enter the off-peak price per kWh to see the difference.
Is my data stored or sent anywhere?
No. Everything runs in your browser.
Is this electricity cost calculator free?
Yes. It is free to use online with no sign-up.
Sources and further reading
- U.S. Department of Energy, Estimating appliance and home electronic energy use.
- U.S. Energy Information Administration, Average price of electricity to customers by state.
- U.S. Environmental Protection Agency, eGRID emissions data.
- ENERGY STAR, Energy efficient products.
Sources were consulted in October 2026. Standards and rules can change, so always check the official page for your situation.