Electricity & Appliance Power Cost Calculator
See what any appliance costs to run per hour, day, month and year. Enter its wattage and daily use, set your electricity rate, and get the energy in kilowatt-hours and the carbon it produces. Build a ledger of several appliances for a running total.
Written by Suhaib Hassan. Rates are examples; use the price on your own bill. Our methodology.
Watts × hours ÷ 1,000 gives kWh per day. Multiply by days and your rate per kWh for the cost.
Small standing loads add up. This shows which devices matter and what a change in use or rate would save.
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kWh per day
kWh per month
kWh per year
kg CO₂ per month
This assumes the appliance draws its rated power the whole time it is on. Thermostat-controlled devices such as heaters and refrigerators cycle on and off, so real use is often lower.
Appliance ledger
Add several appliances to see the combined running cost of a home circuit or a whole room.
| Appliance | Power | Hours / day | Days / mo | kWh / mo | Cost / mo | |
|---|---|---|---|---|---|---|
| Ledger total | — | — | ||||
Typical appliance running costs
Approximate wattages and daily use for common appliances, priced at your rate above. Click a row to load it. Real use varies by model and settings.
| Appliance | Watts | Hours / day | kWh / mo | Cost / mo | Cost / yr |
|---|
How the cost is calculated
Energy
kWh per day = watts × hours ÷ 1,000Cost
cost = kWh per day × days × rateCarbon
kg CO₂ = kWh × emissions factorIf only volts and amps are listed, watts = volts × amps. For example, 120 V × 1.5 A = 180 W.
Vampire loads
Devices in standby can add roughly 5% to 10% of a home's electricity use. At your rate, a device idling all year costs:
Smart power strips, sleep modes and unplugging chargers cut standby waste.
Worked examples
Illustrative devices priced at 16.5¢ per kWh, each checked by hand. The first is the default setup.
Gaming PC, 6 hours a day
450 W, 30 days a month.
× 30 = 81.0 kWh
81.0 × 0.165 = $13.37 a month
× 12 = $160.38 a year
Space heater
1,500 W for 5 hours a day, 30 days.
× 30 = 225 kWh
225 × 0.165 = $37.13 a month
Level 2 EV charger
7,200 W for 2.5 hours a day, 30 days.
× 30 = 540 kWh
540 × 0.165 = $89.10 a month
How to work out what an appliance costs
- Find the power in watts on the label, or multiply volts by amps.
- Estimate hours of use per day and days per month.
- Find your electricity rate per kWh on your bill.
- Multiply energy by the rate. Use a plug-in power meter for the most accurate reading.
Your bill may also include fixed charges and tiered or time-of-use rates, so the true cost of an extra appliance can differ from a flat-rate estimate.
By Suhaib Hassan · Reviewed 29 September 2026 · How CalculatePilot verifies formulas →
Sources
- U.S. Energy Information Administration (EIA), Electric Power Monthly, average residential retail price of electricity by state.
- U.S. EPA, eGRID (Emissions & Generation Resource Integrated Database), national CO₂ output emission rates.
- U.S. Department of Energy, Estimating Appliance and Home Electronic Energy Use.
Frequently asked questions
How do I find my appliance's wattage?
Check the nameplate on the back or underside. If it lists volts and amps, multiply them to get watts. For devices that cycle, such as refrigerators and air conditioners, a plug-in power meter shows real use over time.
What is the difference between peak and off-peak rates?
Time-of-use plans charge more when demand is high, often late afternoon and evening, and less overnight. Running an EV charger, dishwasher or dryer off-peak can cut its cost noticeably if your plan has these tiers.
How is carbon output estimated?
Energy in kWh is multiplied by an emissions factor for the grid. The US average is roughly 0.37 kg of CO₂ per kWh, while the marginal or non-baseload rate is higher at about 0.5 kg. Cleaner grids are much lower. Edit the factor to match your area.
Why does a 1,500 W heater not use 1.5 kWh every hour?
Thermostats switch the heating element off once the room reaches the target temperature. If it runs 30 minutes in an hour, it uses 0.75 kWh. The calculator assumes constant use unless you reduce the hours.
What is a kilowatt-hour?
A kilowatt-hour is the energy used by a 1,000 watt device running for one hour. It is the unit your electricity bill is based on.
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