What a device costs to run comes down to three numbers: how much power it draws, how long it runs, and what your electricity company charges for each kilowatt-hour. Multiply them together and you have the cost, which is all this electricity cost calculator does, one visible line at a time.
Put in the watts, the hours a day and the days a week it is in use, and your price per kWh. It works out the kilowatt-hours a day and a year, the cost of an hour, a month and a year, and how that compares with the national average price and with what an average home uses. The price box starts at EIA's average US residential price, every figure it supplies names its source, and the list of what it cannot tell you is below the answer.
In this guide
The electricity cost calculator
A plug-in power meter gives the real figure. The W on a label or power supply is the most it can draw, so it overstates; the PSU calculator's total is a PC's peak, the cautious figure.
On the days it is used. Put 24 for something that never switches off, such as a router.
7 for every day, 5 for weekdays only, 2 for weekends only.
On your bill: the total charged for electricity divided by the kWh used, so delivery is counted too. 17.23 is EIA's US average residential price for 2025.
How that is worked out, line by line
- Energy on a day it is used1.20 kWh
- Days in use a year365 days
- Energy a year438 kWh
- Cost of one hour of use5.17 cents
- The same year at EIA's 2025 US average price75.47 dollars
- Share of what an average US home buys in a year4.1 %
On those numbers you are in the 50 to 150 dollars a year band, which is the section below.
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Where every number here comes from
No part of this was measured on a bench here. This site works from published specifications and from what owners report, and every number below is either one you typed in or a published figure with its source named next to it.
The figures this page supplies
- Watt-hours in a kilowatt-hour: 1,000. EIA, Electricity explained: measuring electricity. A watt-hour is one watt used for one hour, and a kilowatt is 1,000 watts, so a kilowatt-hour is 1,000 watt-hours.
- Days in a year: 365 days. The calendar's common year. A leap year's extra day is left out, which moves a year's figure by under 0.3%.
- Months in a year: 12. The calendar. A month here is a twelfth of the year, an average, since months run 28 to 31 days.
- Cents in a dollar: 100. 31 U.S.C. 5101: United States money is expressed in dollars, and cents, or hundredths of a dollar.
- EIA's average US residential price, 2025: 17.2300 cents/kWh. EIA Electric Power Monthly, Table 5.3 (released 23 Oct 2026): 17.23 cents per kWh for the residential sector in 2025, a figure EIA marks final. Its preliminary figure for January to August 2026 is 18.19.
- Electricity an average US home buys in a year: 10,791 kWh. EIA FAQ, How much electricity does an American home use?: 10,791 kWh sold to the average US residential customer in 2022, about 899 kWh a month.
Why each step is the step it is
- Energy on a day it is used:
watts * hours / wh_per_kwh. Watts times hours is watt-hours, EIA's own sum (40 W for five hours is 200 Wh); a thousand of them is a kilowatt-hour, the unit a bill charges for. - Days in use a year:
days * days_year / 7. The days a week it is used, spread over a 365-day year. - Energy a year:
kwh_day * days_used. A day's energy times the days it is used. This is the figure to compare devices by. - Cost of one hour of use:
watts / wh_per_kwh * price_c. Kilowatts times one hour is kilowatt-hours, times your price in cents per kWh. - Cost a year:
kwh_year * price_c / cents_per_dollar. The year's kWh times your price per kWh, turned from cents into dollars. - Cost a month, on average:
cost_year / months_year. A twelfth of the year's cost. A real month's bill moves with the days in it and with use. - The same year at EIA's 2025 US average price:
kwh_year * us_avg_c / cents_per_dollar. The same energy at 17.23 cents per kWh, so a price you typed can be set against the national average. - Share of what an average US home buys in a year:
kwh_year / home_kwh * 100. The year's kWh against the 10,791 kWh EIA counts for the average US home, to show how big a part of a bill this device is.
What this cannot tell you
Every calculator has an edge, and a page that hides its edge is worse than no page at all. Here is this one's.
- It is arithmetic on the figures you give it. No device was plugged into a meter for it, and this site has not measured what any device draws.
- It is only as right as the watts. The figure on a label or a power supply is the most a device can draw, and most draw less most of the time, so a label figure overstates the cost; a plug-in power meter reading over a normal day is the figure to use.
- It assumes one steady draw for the hours you give. A PC idling at the desktop draws far less than the same PC in a game, so for mixed use, work out each kind of use on its own and add the costs.
- It counts the hours in use only. Many devices draw a little power while switched off or asleep; to count it, work that standby draw out on its own at 24 hours less the hours in use.
- The default price is a national average. Prices differ a lot from state to state and plan to plan, and some plans charge more at certain hours, so the price on your own bill gives the closer answer.
What that yearly cost means
These follow from the answer above and nothing else. Each heading below covers one span of results, so read the one the calculator pointed you at and ignore the rest.
10 dollars a year or less
Small enough that replacing a working device to save electricity will not pay for itself for many years: divide the price of the new one by what it would save a year. If this is a router or mesh system left on all day, choose the next one on what it does for your home, not on its power.
Best Wi-Fi 7 Mesh System 2026: 3 Picks Worth the Money covers this range in full.
Best WiFi Router for Home in 2026: 5 Ranked Picks covers this range in full.
10 to 50 dollars a year
Worth knowing, rarely worth changing gear for. Check the figure you typed first: a label's watts are the most a device can draw, so a reading from a plug-in meter may put you lower. Hours are the lever you control, since the cost moves with them one for one.
Monitor Buying Guide 2026: The Specs Worth Paying For covers this range in full.
Best Soundbar for TV (2026): 3 Picks by Budget covers this range in full.
50 to 150 dollars a year
This page's own example lands here: a PC drawing 300 W for four hours a day, every day, at the US average price. If that is a gaming PC, the graphics card is usually the part with the largest power rating in it, and the guides below cover choosing one alongside the rest of a build.
How to Build Your First Gaming PC in 2026 Best Parts to Buy covers this range in full.
Best 1440p Gaming PC Build $1200 Parts List (2026) covers this range in full.
More than 150 dollars a year
Worth measuring rather than estimating. Put a plug-in power meter on it for a normal day and use that figure, since a label or power supply rating can overstate the draw a long way. If the figure holds, the hours and the price per kWh are the two numbers that move it.
If the device is a PC you are planning, the PSU calculator adds up its peak draw from the parts. That is the most it can pull, so it gives the highest cost this page would show; a meter reading while you play is the closer figure. An electricity cost calculator can only be as right as the watts and the price you give it, so take the price from your own bill when you have one.
Questions about the electricity cost calculator
How do I calculate the electricity cost of a device?
Multiply its watts by the hours it runs and divide by 1,000 to get kilowatt-hours, then multiply by your price per kWh. The example this electricity cost calculator opens with is a 300 W device used 4 hours a day: 1.2 kWh a day, 438 kWh a year, and at 17.23 cents per kWh that costs 75.47 dollars a year, about 6.29 dollars a month.
How do I work out a device's power consumption in kWh?
Watts times hours gives watt-hours, and 1,000 watt-hours make a kilowatt-hour. EIA's own example is a 40 W bulb used for 5 hours: 0.2 kWh. A 300 W device used 4 hours a day uses 1.2 kWh a day and 438 kWh a year, which is 4.1% of the 10,791 kWh EIA counts for an average US home in a year.
How much does it cost to run a gaming PC?
It depends on what it draws while you play and for how long. At 300 W for 4 hours a day, every day, at EIA's 2025 average of 17.23 cents per kWh, it costs 75.47 dollars a year. A heavier build drawing 500 W for 6 hours a day costs 188.67 dollars a year, and the same 300 W PC played only on weekends costs 21.56 dollars. A plug-in meter reading while you play is the figure to put in.
What price per kWh should I use in an electricity cost calculator?
The one on your own bill: the total charged for electricity, delivery included, divided by the kWh used. Without a bill, EIA's average US residential price for 2025 was 17.23 cents per kWh, the default here. Prices vary widely by state: at 30 cents, the example's 438 kWh a year costs 131.4 dollars instead of 75.47.
How much does it cost to leave a device on all the time?
Put 24 in the hours box. A device drawing 10 W around the clock uses 0.24 kWh a day and 88 kWh a year, which at 17.23 cents per kWh is 15.09 dollars a year. Small, steady draws add up because they never stop, so a router or a device left asleep is worth working out on its own.
Sources
- EIA, Electricity explained: measuring electricity: Defines the watt, the watt-hour (one watt used for one hour) and the kilowatt-hour, and works the sum this page uses: a 40 W bulb used for five hours is 200 Wh, or 0.2 kWh.
- EIA Electric Power Monthly, Table 5.3: average price of electricity to ultimate customers: Gives the average US residential price: 17.23 cents per kWh for 2025 (final) and 16.48 for 2024, the default in the price box.
- EIA Electric Power Monthly, Table 5.6.A: average price of electricity by state: The residential price state by state for the latest month, for a reader who does not have a bill to hand.
- EIA FAQ: how much electricity does an American home use?: 10,791 kWh a year sold to the average US residential customer in 2022, the figure the share line is set against.
- 31 U.S.C. 5101: decimal system: Sets out that United States money is expressed in dollars and cents, hundredths of a dollar.
PSU Calculator 2026: What Power Supply You Actually Need UPS Calculator 2026: How Long Your Battery Actually Lasts
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