How it works
Energy use in kilowatt-hours (kWh) is power in kilowatts multiplied by hours of use. A 100 W device running 4 hours a day for a year uses 100 W × 4 h × 365 / 1000 = 146 kWh. Multiply by your price per kWh (find it on your bill) for the cost.
Where to find the wattage
Look on the label or power adapter, or in the manual. If it lists amps and volts, multiply them (watts = volts × amps). A plug-in energy meter can measure actual use. Appliances with motors or heating elements cycle on and off, so real use may be lower than the rated power.
Biggest savings
- Heating and cooling devices and electric water heaters are usually the largest.
- Replace old bulbs with LEDs.
- Use a power strip to switch off devices with standby drain.
Frequently asked questions
How do I find my electricity price?
Look at your bill for the price per kWh; if you have different peak and off-peak prices, use an average.
Why is my fridge listed at 150 W if it says 600 W on the label?
The label shows peak power; the compressor only runs part of the time, so the average is lower.
What is standby power?
Electricity used by devices that are switched off but still plugged in, such as chargers and TVs.