Energy in kWh = watts × hours ÷ 1,000; cost = kWh × your price per kWh. A 100 W TV used 5 hours a day uses 0.5 kWh a day, or 183 kWh a year. Pick an appliance to start from a typical wattage, change it to the one on your label, and enter your own electricity price in your currency – it is printed on your bill.
Yearly use and cost of common appliances
Typical power and daily use, at three electricity prices (per kWh, in any currency):
| Appliance | kWh a year | at 0.15 | at 0.25 | at 0.35 |
|---|---|---|---|---|
| Refrigerator (daily average 50 W) | 438 | 66 | 110 | 153 |
| TV, 100 W, 5 h a day | 183 | 27 | 46 | 64 |
| Air conditioner, 1,100 W, 6 h a day | 2,409 | 361 | 602 | 843 |
| Space heater, 1,500 W, 4 h a day | 2,190 | 329 | 548 | 767 |
| Tumble dryer, 3,000 W, 1 h a day | 1,095 | 164 | 274 | 383 |
| Gaming PC, 400 W, 4 h a day | 584 | 88 | 146 | 204 |
| Wi-Fi router, 10 W, all day | 88 | 13 | 22 | 31 |
| LED bulb, 9 W, 6 h a day | 20 | 3 | 5 | 7 |
| Electric car charger, 7.4 kW, 2 h a day | 5,402 | 810 | 1,351 | 1,891 |
Heating, cooling and drying are where the money goes: in the table, the space heater uses more than four times as much as the TV, the router and ten LED bulbs put together (2,190 kWh against 467).
Why the price matters as much as the appliance
Electricity prices differ widely between countries, and between night and day tariffs in the same home. The same space heater costs 329 a year at 0.15 per kWh and 767 at 0.35. Use the price per kWh from your latest bill, including taxes and fees, and remember that a fixed daily standing charge does not change with how much you use.
Using less
- Heat and cool the person, not the room: an electric blanket or a fan uses a fraction of the power of a heater or an air conditioner.
- Dry outside or on a rack when you can: a tumble dryer is one of the most power-hungry appliances in a home.
- Charge an electric car on a cheaper night tariff, where one is available.
- Swap the last halogen or incandescent bulbs for LED: a 60 W bulb replaced by a 9 W LED saves about 85% of the lighting energy.
- Look at what stays on all day: a device drawing 15 W around the clock uses 131 kWh a year.
Watts, kilowatts and kWh
Power (watts) is how fast an appliance uses energy; energy (kWh) is how much it used over time. A 2,000 W kettle that boils for 3 minutes uses only 0.1 kWh, while a 10 W router left on for a year uses 88 kWh. Duration matters as much as power.
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Frequently asked questions
How do I calculate the electricity cost of an appliance?
Multiply its power in watts by the hours you use it, divide by 1,000 to get kWh, then multiply by your price per kWh. A 1,500 W heater for 4 hours uses 6 kWh; at 0.25 per kWh that is 1.50 a day.
Where do I find the wattage?
On the rating label, usually on the back or underneath, or in the manual. It may be in watts (W) or kilowatts (kW): 1 kW = 1,000 W.
Why does my fridge use less than its label says?
Fridges, freezers, heaters and air conditioners switch on and off with a thermostat. The label shows the power when running, but the average over a day is much lower. Use the energy label's yearly kWh if you have it.
What is a kilowatt-hour?
The energy used by something drawing 1,000 watts for one hour. It is the unit on your electricity bill everywhere in the world.
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