Appliance Energy Cost Calculator
Calculate how much energy an appliance uses and what it costs to run from its wattage, hours of use per day, and your electricity rate.
How to use this tool
- Read the appliance's wattage from its label or spec sheet.
- Estimate how many hours per day it actually runs.
- Enter the number of days to total (30 for a month, 365 for a year).
- Enter your electricity rate in dollars per kWh.
- Read the energy used in kWh and the running cost.
Find out what any appliance really costs to run. Enter its wattage, how many hours a day you use it, and your electricity rate to see the energy used and the dollar cost.
Formula
Convert watts to kilowatts, multiply by run-time, then by your rate:
Energy (kWh) = (Watts ÷ 1000) × Hours/day × Days
Running cost = Energy (kWh) × Rate
How it works
The cost of running any electrical device comes down to one chain of conversions. An appliance's wattage is its rate of energy use; dividing by 1,000 converts watts to kilowatts. Multiplying by the hours it runs per day and the number of days gives total energy in kilowatt-hours — exactly how utilities meter and bill electricity. Pricing those kWh at your rate gives the dollar cost.
Use the nameplate wattage from the appliance label for a worst-case estimate. Many devices draw less than their rating because they cycle on and off (a refrigerator, an AC compressor) or modulate power. For those, either lower the hours to the actual compressor run-time or use a measured average wattage from a plug-in power meter.
This model assumes a steady wattage over the hours entered. For appliances rated in amps and volts instead of watts, multiply amps by volts to get watts first. The reference table below shows annual energy and cost for several common household devices at a $0.15/kWh rate.
Worked example
A 1,500 W space heater, 3 h/day for 30 days at $0.15/kWh
- Power in kW = 1,500 W ÷ 1000 = 1.5 kW.
- Energy = 1.5 kW × 3 h × 30 days = 135 kWh.
- Running cost = 135 kWh × $0.15 = $20.25.
Energy used 135.00 kWh | Running cost $20.25
Annual energy and cost of common appliances (at $0.15/kWh)
| Appliance (watts, hours/day) | Annual energy | Annual cost |
|---|---|---|
| LED bulb (10 W, 5 h/day) | 18 kWh | $2.74 |
| Refrigerator (150 W, 24 h/day) | 1,314 kWh | $197.10 |
| Window AC unit (1000 W, 8 h/day) | 2,920 kWh | $438.00 |
| Space heater (1500 W, 4 h/day) | 2,190 kWh | $328.50 |
| Desktop PC (200 W, 6 h/day) | 438 kWh | $65.70 |
Key terms
- Watt (W)
- A unit of power — the rate of energy use. A 1,000 W device uses one kilowatt-hour of energy each hour it runs.
- Kilowatt-hour (kWh)
- Energy equal to one kilowatt sustained for one hour. It is the unit utilities bill.
- Nameplate rating
- The maximum power draw printed on an appliance's label. Actual average draw is often lower for cycling devices.
- Duty cycle
- The fraction of time an appliance actually draws power. A fridge with a 30% duty cycle runs its compressor about 7 hours out of 24.
Frequently asked questions
- How do I find an appliance's wattage?
- Look for a watts (W) rating on the label, manual, or spec sheet. If it lists amps (A) and volts (V) instead, multiply them: watts = amps × volts. A plug-in power meter gives the most accurate real-world figure.
- Why does my fridge cost less than this says?
- Refrigerators and air conditioners cycle their compressors on and off, so they don't draw full wattage 24/7. Use the compressor's actual run-time hours, or a measured average wattage, rather than nameplate watts times 24.
- What uses the most electricity at home?
- Heating and cooling, water heating, and electric clothes drying are typically the biggest loads, followed by refrigeration and always-on electronics. High-wattage devices used for many hours dominate the bill.