Electricity cost calculator

Enter the wattage and how long you use anything that plugs in, and see what it costs per hour, day, month and year at your state's electricity rate.

Official EIA data · August 2026

Wattage

Hours per day

Days per month

days

Find the watts on the label or nameplate. If it only lists amps, multiply by the voltage: most U.S. outlets are 120 V, large appliances 240 V.

Electricity rate

EIA average residential price, August 2026. Your bill shows your exact rate.

Cost to run this device per month

$2.18

12 kWh at 18.16¢/kWh (U.S. average)

Per hour of use: $0.02
Per day of use: $0.07
Per year (same use every month): $26.15

Power draw

100 W

0.1 kW

Energy per year

144 kWh

if used like this all year

Full details Costs in every state, real-world usage, formula and tips

The formula

Cost = watts × hours ÷ 1,000 × price per kWh

This is the Department of Energy's method. DOE's own example: a 1,500 W kettle used 1 hour a day for a year uses 547.5 kWh, which costs $60.23 at 11¢/kWh. At today's U.S. average of 18.16¢, the same kettle costs $99.43 a year.

Cost per hour by wattage

At the U.S. average residential rate for August 2026.

Wattage	kWh per hour	Cost per hour	8 h a day for a month
10 W	0.01	$0.00	$0.44
60 W	0.06	$0.01	$2.62
100 W	0.1	$0.02	$4.36
500 W	0.5	$0.09	$21.79
1,000 W	1	$0.18	$43.58
1,500 W	1.5	$0.27	$65.38
3,000 W	3	$0.54	$130.75
5,000 W	5	$0.91	$217.92

Phantom loads

Many electronics keep drawing a little power when switched off: TVs, consoles, chargers, microwaves with clocks. A few watts around the clock add up: 5 W continuously is 3.65 kWh a month. Plugging them into a power strip you switch off removes that load.

Quick answers

How do I calculate the cost of electricity for an appliance?

Multiply the wattage by the hours used and divide by 1,000 to get kWh, then multiply by your rate. Example: a 100 W device for 4 hours a day uses 0.4 kWh a day, 12 kWh a month, which costs $2.18 at the U.S. average of 18.16¢/kWh.

How do I find how many watts something uses?

Look at the label or nameplate, usually on the back or bottom. If it lists amps instead, multiply amps by volts (120 V for most outlets). A plug-in electricity usage monitor measures the real draw of anything that plugs into a 120 V outlet.

What is a kilowatt-hour?

A kilowatt-hour (kWh) is 1,000 watts used for one hour. It is the unit on your electric bill. A 100 W bulb left on for 10 hours uses 1 kWh.

Why is my real cost lower than the calculation?

The label shows maximum power. Devices with thermostats or variable settings, like refrigerators, heaters on low or fans on a slow speed, draw less most of the time. DOE suggests counting a refrigerator's running time as about a third of the time it is plugged in.

Sources

Last reviewed November 2, 2026. Rates refreshed automatically when EIA publishes a new month.

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See everything

These are estimates. State rates are EIA averages (total residential revenue ÷ kWh sold), so they include fixed monthly charges spread across usage; your own price per kWh, time-of-use rates and taxes can differ. Real appliance use depends on the model, settings, climate and habits.