Electricity cost calculator for appliances
Enter the wattage, how long the appliance runs and your electricity rate – the calculator shows energy use and running cost per day, month and year straight away. Add standby power to include the rest of the time it stays plugged in.
Example: Power when running 100 W · Hours of use per day 4 hours · Days of use per week 7 days · Electricity rate 0.1831 per kWh → Cost per year: 26.73. Source: U.S. Energy Information Administration – Electric Power Monthly, Table 5.6.A, Residential, U.S. Total, July 2026 (preliminary): 18.31 ¢/kWh (retrieved 2026-09-27). Updated: .
How it is calculated
How to calculate electricity cost from watts
Energy is power multiplied by time: kWh = watts × hours ÷ 1,000. The cost is kWh × price per kWh. A 100 W appliance running for 4 hours uses 400 Wh, or 0.4 kWh.
How to calculate electricity cost
- Enter the power when running in watts (rating label or plug-in meter).
- Set the hours of use per day and days of use per week.
- Enter your electricity rate per kWh and, optionally, standby power – usage and cost per day, month and year appear instantly.
The calculator works from one week: hours of use = hours per day × days per week. It scales up with 365 ÷ 7 weeks per year; a month is one twelfth of the year and a day is one 365th. Daily figures are therefore averages over every calendar day, including days the appliance is not used.
Worked examples (rate 0.1831/kWh)
| Appliance | Use | kWh per year | Cost per year |
|---|---|---|---|
| TV 100 W | 4 hours a day | 146 kWh | 26.73 |
| TV 100 W + 0.5 W standby | 4 hours a day, standby otherwise | 149.65 kWh | 27.40 |
| Washing machine 2,000 W | 1 hour on 3 days a week | 312.86 kWh | 57.28 |
| Desktop PC 300 W | 8 hours on 5 days a week | 625.71 kWh | 114.57 |
TV with standby, step by step: 4 hours × 7 days = 28 hours of use per week, leaving 168 − 28 = 140 hours on standby. Per week: 100 W × 28 h = 2.8 kWh plus 0.5 W × 140 h = 0.07 kWh. Per year: 2.87 kWh × 365 ÷ 7 = 149.65 kWh, of which 3.65 kWh is standby. Cost: 149.65 kWh × 0.1831 = 27.40 (standby share 0.67).
Standby rule of thumb: 1 watt drawn around the clock is 8,760 hours × 1 W = 8.76 kWh a year – about 1.60 per watt per year at 0.1831/kWh.
Which numbers to enter
Wattage: The rating label usually shows maximum power. Appliances with a heater or compressor (washer, fridge, dryer) only draw it some of the time. For those, the yearly kWh on the EnergyGuide label is more accurate, and a plug-in power meter shows actual use.
Electricity rate: The default is the U.S. average residential price from the U.S. Energy Information Administration (Electric Power Monthly, Table 5.6.A, July 2026, preliminary): 18.31 cents per kWh. Rates vary widely by state and season, so use the price per kWh from your own bill for a precise figure. Outside the U.S., enter your local rate – the result is in the same currency.
This is an estimate assuming steady use. It does not model varying power draw, time-of-use tariffs, fixed monthly charges or future price changes.
More cost calculators: see what charging an electric car costs with the EV charging cost calculator, price a road trip with the gas cost calculator, and see how rising prices erode your money with the inflation calculator.
Frequently asked questions
How do I convert watts to cost?
Watts × hours ÷ 1,000 gives kWh, and kWh × your rate gives the cost. 100 W for 4 hours a day is 0.4 kWh a day, 146 kWh a year and 26.73 a year at 0.1831/kWh.
What is the average price of electricity per kWh in the U.S.?
The EIA reports an average residential price of 18.31 cents per kWh for July 2026 (preliminary). Your own rate depends on your state, utility and plan.
How much does standby power cost?
Each watt of standby around the clock is 8.76 kWh a year, about 1.60 at 0.1831/kWh. A TV with 0.5 W standby that runs 4 hours a day uses 3.65 kWh on standby – 0.67 a year.
How much does it cost to run a computer per month?
A 300 W desktop running 8 hours on 5 days a week uses 625.71 kWh a year, which is 52.14 kWh and 9.55 a month at 0.1831/kWh.
Why is my measured usage lower than the label?
The label usually states peak power. Many appliances run below it or cycle on and off, like fridges and washing machines. A plug-in power meter or the EnergyGuide label gives a more realistic yearly figure.
Can I use it with pounds, euros or rupees?
Yes. Replace the rate with your local price per kWh; the costs are then in that currency. The results are shown as plain numbers without a currency symbol.
Sources and legal basis
As of: · Editorial policy
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