How to calculate what an appliance costs to run

By Felipe Guilherme de Oliveira Bueno. Updated November 11, 2026.

You need two numbers: how much electricity the appliance uses, and what your utility charges for it.

Step 1: find the energy use in kWh

For anything that runs at a steady power, multiply the watts by the hours you use it and divide by 1,000.

Watts x hours / 1,000 = kWh

A 1,500-watt space heater used 4 hours a day uses 1,500 x 4 / 1,000 = 6 kWh a day.

The watts are printed on the nameplate, usually on the back or bottom, and in the manual. If the plate shows only amps, multiply amps by the voltage (120 volts for a standard U.S. outlet) for an upper estimate.

Step 2: multiply by your rate

kWh x price per kWh = cost

At the U.S. average residential rate of 18.19 cents per kWh, those 6 kWh cost $1.09 a day, or about $32.74 over a 30-day month. In Hawaii, at 46.41 cents, the same month costs $83.54. In North Dakota, at 12.46 cents, it costs $22.43.

Why this does not work for a refrigerator

Refrigerators, freezers, dehumidifiers and air conditioners cycle on and off. The nameplate watts tell you the peak draw, not the average. For these, use the yearly kWh from the yellow EnergyGuide label or from the certified product list, which is what this site does.

When you want the real number

A plug-in electricity monitor sits between the appliance and the outlet and counts the kWh it actually uses. Leave it for a week, including a weekend, and scale up.

Use the calculator to run the numbers with your state rate.

How we get these numbers: yearly electricity use comes from the ENERGY STAR certified product lists, measured with the federal test procedure. The rate is the average residential price the U.S. Energy Information Administration reports for each state, January to August 2026. Your own bill depends on your utility, your plan and how you use the appliance. See sources.