How to use the electricity cost calculator
- Find the power in watts (W) on the appliance's label, its charger or its manual. 1.5 kW is 1500 W. If the label gives amps and volts instead, choose Amps and volts.
- Enter how long it runs: hours per day, and days per week. 30 minutes is 0.5 hours; 7 days means every day.
- Enter how many if you have several of the same, such as six light bulbs.
- Enter your price per kWh from your electricity bill, as dollars (or pounds) and cents. 18 cents is 0.18.
The result shows the electricity used and the cost per hour of use, per day it is used, per month and per year. The currency sign follows your browser's language setting.
How the cost is worked out
Electricity is billed in kilowatt-hours (kWh). The U.S. Energy Information Administration explains that "One kilowatt is equal to 1,000 Watts" and "One kWh is one kilowatt generated for one hour". So:
- kWh = watts x hours / 1000
- Cost = kWh x price per kWh
The EIA's own example: a 40 W bulb used for five hours uses 200 Wh, or 0.2 kWh. For longer periods the calculator takes a year as 365 days and a month as one twelfth of a year (about 30.4 days):
- Per year = kWh per day x days used per week / 7 x 365
- Per month = per year / 12
Example: a 1500 W space heater running 4 hours a day, every day, at 18 cents per kWh. Press Try an example to see it. If your browser is set to UK English, the example is a 100 W TV used 5 hours a day at 26.32p per kWh instead.
| Period | Working | kWh | Cost |
|---|---|---|---|
| Per hour | 1500 x 1 / 1000 | 1.5 | $0.27 |
| Per day | 1500 x 4 / 1000 | 6 | $1.08 |
| Per month | 2,190 / 12 | 182.5 | $32.85 |
| Per year | 6 x 365 | 2,190 | $394.20 |
A heater with a thermostat switches on and off, so it may draw full power for less time than it is switched on. Enter the hours it actually runs if you know them; otherwise treat the result as an upper figure.
Where to find your price per kWh
Your electricity bill shows the price per kWh, sometimes called the unit rate or energy charge. If the bill lists more than one charge per kWh, for example one for supply and one for delivery, add them together. Fixed daily or monthly charges do not depend on how much you use, so leave them out: the calculator works out only what the appliance adds.
If you do not have a bill to hand, the calculator can fill in an official average. These are averages, so your own rate may be higher or lower.
| Where | Price per kWh | Period | Source |
|---|---|---|---|
| United States, homes | 18.31 cents | July 2026 | EIA Electric Power Monthly, Table 5.6.A, U.S. Total, residential |
| England, Scotland and Wales | 26.32 pence | 1 October to 31 December 2026 | Ofgem energy price cap |
The EIA figure is the average price paid by US homes in July 2026, published on 24 September 2026. Prices differ a lot by state. Ofgem's figure is for a standard variable tariff paid by Direct Debit: "If you are on a standard variable tariff (default tariff) and pay for your electricity by Direct Debit, you will pay on average 26.32 pence per kilowatt hour (kWh)." Ofgem adds that "The government has removed VAT from electricity bills from 1 October 2026 to 31 March 2027", and the cap also has a daily standing charge of 54.83 pence, which this calculator does not include. In pounds, 26.32p is 0.2632.
Amps and volts to watts
Some labels give the current in amps (A) and the voltage in volts (V) instead of watts. Multiplying them gives an estimate of the power: watts = amps x volts. A label of 10 A at 120 V gives 1,200 W.
For heaters, kettles and other appliances that simply heat, that is close to the real figure. For motors and electronics the real power can be lower than amps x volts. If the label also gives watts, use the watts.
Why your bill may differ
- Appliances that cycle, such as fridges, freezers and air conditioners, do not run at full power all the time. A plug-in energy meter shows the kWh they really use.
- Standby power adds up for devices left plugged in. Enter the standby watts and 24 hours if you want to see it.
- Time-of-use tariffs charge different prices at different times of day. Use the price for the hours the appliance runs.
- Fixed charges and taxes are on your bill whatever you use, and are not part of this estimate.
Questions and answers
How do I calculate kWh?
Multiply the watts by the hours and divide by 1,000. A 100 W TV used for 5 hours uses 100 x 5 / 1000 = 0.5 kWh.
How much does it cost to run a 1500 watt heater?
It uses 1.5 kWh in each hour it runs at full power. At 18 cents per kWh that is 27 cents an hour, or $1.08 for 4 hours. Use your own price per kWh from your bill.
What is the average price of electricity per kWh in the US?
The EIA reports an average residential price of 18.31 cents per kWh for the United States in July 2026. Prices vary a lot by state and by month, so your bill is the best guide.
What is the UK electricity price cap per kWh?
Ofgem says that from 1 October to 31 December 2026, people on a standard variable tariff paying by Direct Debit pay on average 26.32 pence per kWh, plus a standing charge of 54.83 pence a day. It is an average across England, Scotland and Wales.
How do I convert amps to watts?
Multiply amps by volts. 10 A at 120 V is 1,200 W, and 5 A at 230 V is 1,150 W. For motors and electronics this can be higher than the real power, so use the watt figure on the label when there is one.
Sources
Checked on 7 October 2026. If a rule has changed, please tell us.