Electricity Cost Calculator
The wattage on the label and the tariff on your bill are all you need to know what any appliance really costs. This electricity cost calculator converts watts and hours into kWh and money per day, month and year.
Use it to find the expensive devices in your home — heaters, dryers and old fridges usually top the list.
Enter valid values to see the results.
Formula
One kilowatt-hour is a 1,000 W appliance running for one hour. Find your tariff on your electricity bill (average US ≈ $0.15/kWh, EU ≈ $0.25–0.35/kWh).
How to measure
- Find the appliance wattage on its label or manual. For devices with cycles (fridge, washer), use a plug-in power meter for a real average.
- Estimate honest daily hours — a TV “on all evening” is usually 4–5 hours.
- Copy the tariff from your bill, including taxes and delivery charges for accuracy.
Worked example
Practical tips
- Heating and cooling dominate bills: space heaters, AC and water heaters are 60–70% of a typical home’s use.
- A plug-in power meter ($15–25) pays for itself by finding phantom loads — devices drawing power while “off”.
- LED bulbs use 8–10 times less than incandescent for the same light; swapping 10 bulbs saves $50–100 a year.
- Running the washer and dishwasher at night helps only if your tariff has off-peak rates.
Waste allowance
Not applicable — but remember real consumption varies: fridges cycle on and off, so their label wattage overstates average use by about 60%.
Typical appliance power and monthly cost (at $0.15/kWh)
| Appliance | Power | Cost / month |
|---|---|---|
| LED bulb (5 h/day) | 10 W | $0.23 |
| Refrigerator | 150 W avg | $16 |
| Air conditioner 12k BTU | 1,200 W | $54 (5 h/day) |
| Electric heater | 2,000 W | $90 (5 h/day) |
| EV charger (daily 20 kWh) | 7 kW | $90 |
Common mistakes
- 1 Using the tariff without taxes and delivery fees — the real per-kWh price is often 20–40% higher than the headline rate.
- 2 Assuming label wattage equals average draw; motors and compressors cycle, heaters with thermostats switch off.
- 3 Forgetting standby loads: a house full of “off” devices can draw 50–100 W around the clock.
- 4 Comparing appliances by wattage alone — a 1,500 W heater used 1 hour costs less than a 100 W fridge running 24/7.
Frequently asked questions
How do I calculate kWh from watts?
Multiply watts by hours of use and divide by 1,000. A 100 W bulb on for 10 hours uses 1 kWh.
How much does a 1,500 W heater cost to run?
1.5 kWh per hour. At $0.15/kWh that is $0.23 per hour, about $34 per month at 5 hours a day.
What uses the most electricity in a house?
Heating and cooling (40–50%), water heating (15–20%), then washer/dryer, fridge and lighting. Electronics are usually under 10%.
How much is 1 kWh?
It depends on your tariff: about $0.10–0.20 in most of the US, $0.25–0.40 in much of Europe. Check your bill for the exact rate including fees.
Do devices use power when off?
Many do — standby draw is 1–10 W per device. TVs, game consoles and chargers add up to $20–50 per year in a typical home.