Every appliance's running cost comes down to three numbers: how much power it draws, how long it runs, and what your utility charges per kilowatt-hour. This electricity cost calculator multiplies them for you and shows the energy used and the cost per day, month and year — handy for comparing a space heater with a heat pump, deciding whether to replace an old fridge, or estimating the cost of a new gadget.
How to use the electricity cost calculator
- Enter the appliance's power in watts (or kilowatts) from its label.
- Enter how many hours a day it runs.
- Enter the number of identical devices, such as light bulbs.
- Enter your electricity rate per kWh from your bill. The default is only an example.
Electricity cost formula
Cost per day = kWh per day × price per kWh
Cost per month = cost per day × 30 · Cost per year = cost per day × 365
Worked example: a space heater
- A 1,000 W space heater runs 3 hours a day.
- Energy: 1,000 × 3 ÷ 1,000 = 3 kWh per day
- At $0.15 per kWh: 3 × 0.15 = $0.45 per day
- Per month: 0.45 × 30 = $13.50; per year: 0.45 × 365 = $164.25
Cost per hour by wattage
Cost of running for one hour at three example rates.
| Power | kWh per hour | $0.10/kWh | $0.15/kWh | $0.25/kWh |
|---|---|---|---|---|
| 10 W | 0.01 | $0.001 | $0.0015 | $0.0025 |
| 60 W | 0.06 | $0.006 | $0.009 | $0.015 |
| 100 W | 0.1 | $0.01 | $0.015 | $0.025 |
| 500 W | 0.5 | $0.05 | $0.075 | $0.125 |
| 1,000 W | 1.0 | $0.10 | $0.15 | $0.25 |
| 1,500 W | 1.5 | $0.15 | $0.225 | $0.375 |
Getting an accurate estimate
- Cycling appliances like refrigerators, freezers and air conditioners run only part of the time. Use the hours the compressor actually runs, or the annual kWh figure on an EnergyGuide label.
- Standby power adds up: devices that stay “on” around the clock use energy 24 hours a day.
- Tiered and time-of-use rates charge different prices at different times or usage levels; use the rate that applies when the device runs.
Ways to cut appliance running costs
The biggest savings come from devices that run many hours or draw a lot of power: heating and cooling, water heaters, clothes dryers, and older refrigerators and freezers. Replacing a 60 W incandescent bulb with a roughly 9 W LED that gives similar light cuts that bulb's energy use by about 85%. Smart plugs or power strips can switch off standby loads overnight. For large appliances, compare the yearly kWh on EnergyGuide labels: a difference of 300 kWh a year is $45 a year at $0.15 per kWh, which adds up over a fridge's long life.
Sizing an air conditioner? The BTU Calculator recommends a capacity for your room.
Frequently asked questions
How do I calculate electricity cost?
Multiply watts by hours of use and divide by 1,000 to get kilowatt-hours (kWh), then multiply by your price per kWh. A 1,000 W heater running 3 hours uses 3 kWh; at $0.15 per kWh that's $0.45 a day.
What is a kilowatt-hour?
A kilowatt-hour is the energy used by a 1,000-watt device running for one hour. Utilities bill electricity by the kWh.
Where do I find my electricity rate?
On your electric bill, usually as a price per kWh. Some bills split it into generation, delivery and other charges — add the per-kWh charges together for the most accurate figure. Fixed monthly fees don't change with usage.
How do I find an appliance's wattage?
Check the nameplate label, the manual or the manufacturer's spec sheet. If only amps and volts are listed, multiply them (watts ≈ volts × amps). A plug-in energy monitor measures real use most accurately.
Why is my real cost different?
Many appliances don't draw full power all the time. Refrigerators and air conditioners cycle on and off, and heaters with thermostats run below their rated wattage on average. For those, estimate the hours the motor or element is actually running.