Electricity Cost Calculator
Wondering what that space heater or old fridge really costs? Enter the wattage, how many hours a day it runs and your electricity rate to see the cost per day, per month and per year.
Estimated Electricity Cost
How It Works
Electricity is billed in kilowatt-hours (kWh): one kWh is what a 1,000-watt appliance uses in one hour. Daily energy is watts × hours per day ÷ 1,000, and cost is kWh × cents per kWh ÷ 100. The same maths is repeated for your chosen period and for a full year, so you can see both the daily figure and the yearly total.
The hours matter as much as the wattage: a 1,500-watt heater run for one hour a day costs a quarter of what it costs at four hours a day. The biggest savings usually come from using a device less, not from replacing it with a slightly more efficient one.
Worked Example
A 1,500-watt heater running 4 hours a day uses 1,500 × 4 ÷ 1,000 = 6 kWh a day. At 15 cents per kWh that is 6 × $0.15 = $0.90 a day — 180 kWh and $27.00 over 30 days, and 2,190 kWh and $328.50 over a full year.
Assumptions
- The appliance draws its full rated wattage the whole time it is on.
- It is used the same number of hours every day in the period.
- Your electricity rate stays the same; time-of-use tariffs are not modelled.
- A year is counted as 365 days.
Monthly cost at 8 hours a day, 30 days, 15¢ per kWh:
| Appliance wattage | kWh per month | Cost per month |
|---|---|---|
| 10 W (LED bulb) | 2.4 kWh | $0.36 |
| 60 W (old bulb) | 14.4 kWh | $2.16 |
| 100 W (fan / TV) | 24.0 kWh | $3.60 |
| 1,500 W (space heater) | 360.0 kWh | $54.00 |
How to Use This Calculator
Enter the wattage, hours per day, number of days, and your rate in cents per kWh. Results update live, showing kWh and cost per day, for your period, and per year.
Tips and Practical Advice
Start with heaters and coolers — they use far more power than lights and chargers, so one hour less a day saves more than unplugging every phone charger in the house. Check the rate on your actual bill: taxes and delivery charges are often bundled into the per-kWh figure. And remember that many appliances cycle — a fridge rated at 150 watts runs its compressor only part of the time, so enter the hours it actually runs.
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