Appliance Energy Cost Calculator
An appliance energy cost calculator estimates how much it costs to run a device based on its power draw and your electricity rate. The method is the one the US Department of Energy describes for estimating appliance operating cost: find the energy used in kilowatt hours, then multiply by the price you pay per kilowatt hour. This tool takes the appliance wattage, the hours it runs each day, the number of days, and your electricity rate, then converts watts and hours into kilowatt hours and multiplies by the rate to return the cost. Every input is editable so you can model anything from a light bulb to a clothes dryer over a day, a month or a year, at your own utility tariff. Knowing the running cost helps you decide whether to replace an old appliance, judge the payback of an efficient model, or simply understand a high electricity bill. The wattage is often printed on the appliance label or in its manual; the rate appears on your utility bill. Every figure is computed deterministically from the formula shown below, with a worked example that reconciles exactly to the calculator so you can follow each step yourself.
Running cost converts watts and hours to kilowatt hours, then prices them: cost = watts / 1,000 x hours x days x rate. A 1,500 W appliance running 4 hours a day for 30 days at $0.15/kWh costs $27.00.
Appliance energy cost formula
Energy (kWh) = W / 1,000 x H x D
W = power draw (watts)
H = hours run per day
D = number of days
Cost = Energy x rate
Watts divided by 1,000 gives kilowatts; multiplied by hours and days gives kilowatt hours, the unit your utility bills. Multiplying by the rate gives the dollar cost.
Worked example
A 1,500 watt space heater runs 4 hours a day for 30 days at an electricity rate of $0.15 per kilowatt hour.
- Daily energy = 1,500 / 1,000 x 4 = 6 kWh
- Over 30 days = 6 x 30 = 180 kWh
- Cost = 180 x 0.15 = $27.00
Running this appliance for the month costs $27.00. These are the calculator's default inputs, so the result above matches the widget exactly.
Appliance Energy Cost Calculator: frequently asked questions
How do I find an appliance's wattage?
The wattage is usually printed on a label on the appliance or in its manual, sometimes as amps and volts (watts equal amps times volts). For devices that cycle on and off, such as refrigerators, use the average power or the annual kilowatt hour figure on the energy guide label instead.
What is a kilowatt hour?
A kilowatt hour (kWh) is the energy used by a 1,000 watt device running for one hour. It is the unit utilities bill you in. A 1,500 watt appliance running for one hour uses 1.5 kWh. Multiplying kilowatt hours by your rate gives the cost.
Where do I find my electricity rate?
Your electricity rate per kilowatt hour appears on your utility bill, often as a supply charge plus delivery charges. Add those components for the full marginal rate. Rates vary widely by region and time of day, so use your own bill rather than a national average for an accurate estimate.
Does standby power matter?
Yes, for many devices. Electronics that stay plugged in draw a small standby load even when off, which adds up across a home over a year. To include it, estimate the standby watts and the hours the device sits idle, then run them through the same formula.
How can I lower running cost?
Reduce run hours, replace high-wattage appliances with efficient models, and shift use to off-peak periods if your rate varies by time of day. The US Department of Energy publishes appliance efficiency guidance and energy saving tips that can cut the kilowatt hours in this calculation.
Official sources
- Estimating appliance energy use and operating cost: US Department of Energy (DOE). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.