How to calculate the electricity cost of an appliance
kWh = power (kW) × hours of use · Cost = kWh × price per kWh
The power is printed on the label in watts (W); divide it by 1,000 to get kilowatts (kW). Multiply by the hours you use it and you get the energy in kilowatt-hours (kWh), which is what your utility charges you for.
Example · a gaming PC
450 W = 0.45 kW. Four hours a day for 30 days: 0.45 × 4 × 30 = 54 kWh a month. At $0.17 per kWh: $9.18 a month, about $110 a year.
Which appliances use the most electricity?
Anything that heats or cools: central AC, space heaters, electric water heaters, clothes dryers, ovens and EV chargers. Small devices that are always on (fridge, router, devices on standby) also add up: a 10 W router uses about 7 kWh a month.
| Appliance | Typical power | Typical use | kWh/month |
|---|---|---|---|
| Central AC | 3,500 W | 6 h/day | 630 |
| Space heater | 1,500 W | 4 h/day | 180 |
| Refrigerator | 150 W | 8 h/day running | 36 |
| Clothes dryer | 3,000 W | 12 loads | 36 |
| LED bulb | 9 W | 5 h/day | 1.4 |
Frequently asked questions
Why is my bill higher than this?
Your bill also includes fixed monthly charges, delivery or standing charges, taxes and sometimes peak-time rates. This calculator estimates the energy each appliance uses.
Is it worth switching to LED bulbs?
Yes: a 9 W LED gives the same light as a 60 W incandescent bulb. At 5 hours a day, it drops from 9 kWh to 1.4 kWh a month per bulb.