Watts, hours and your rate — the one calculation
Watts is power (how hard the device pulls right now); a kilowatt-hour is energy (power kept up over time). Turning watts into kWh is the whole job: divide watts by 1000, multiply by hours run, multiply by your price per kWh. The US average rate is about 18 cents/kWh in 2026, but it runs from roughly 12 cents in Louisiana to over 31 cents in Massachusetts.
What common appliances cost to run
| Appliance | Typical watts | Use | Cost / month* |
|---|---|---|---|
| LED bulb | 10 W | 3 h/day | $0.14 |
| LCD TV | 100–200 W | 4 h/day | $1.90–3.80 |
| Microwave | 800–1000 W | 0.5 h/day | $1.15–1.45 |
| Washing machine | 500–1000 W | 1 h/day | $2.40–4.80 |
| Electric oven | 2000–3000 W | 1 h/day | $9.60–14.40 |
| Clothes dryer | 2000–5000 W | 0.5 h/day | $4.80–12.00 |
| Air conditioner | 3000–3500 W | 6 h/day | $26–31 |
*At $0.16/kWh. Scale by your own rate: at 31 cents these numbers nearly double.
Where the number goes wrong
- Watts are not kWh. Watts is instantaneous power; kWh is power over time. A 2000 W kettle run for half an hour uses just 1 kWh.
- Cycling appliances. A fridge or AC rated at 150–250 W only draws that when the compressor is on, so use its average duty, not the nameplate, for a realistic monthly figure.
- Standby draw adds up. A TV, receiver and router idling at ~20 W together cost around $27 a year doing nothing useful.
Common questions
How do I work out the cost of running an appliance?
Divide the wattage by 1000 to get kilowatts, multiply by the hours you run it, then multiply by your price per kWh. A 1500 W heater for 4 hours at 16 cents is 1.5 x 4 x 0.16 = 96 cents.
What is a kilowatt-hour?
A kilowatt-hour (kWh) is the energy used by a 1000 watt device running for one hour. It is the unit your utility bills you in. One kWh equals a 100 W bulb left on for 10 hours.
Why does the nameplate wattage overstate the cost?
Appliances that cycle, like a fridge or an air conditioner, only draw full power part of the time. A 150 W fridge runs roughly a third of the time, so its real average draw is closer to 50 W.
