About the Electricity Cost Calculator
This electricity cost calculator shows exactly what a device costs to run. Enter its power draw in watts, how many hours a day and days a week you use it, and the price you pay per kilowatt-hour, and it returns the energy used and the cost per hour, per day of use, per month and per year.
Use it to find the energy hogs in your home — space heaters, gaming PCs, dehumidifiers, pool pumps, crypto rigs, aquarium heaters — or to compare two appliances before you buy. Set the quantity above one to price a group of identical devices, such as several fans or monitors, in one go.
The result assumes the device draws its rated wattage the whole time it is on. Many appliances cycle (fridges, heaters with thermostats, AC) or run below their label rating, so a plug-in watt meter reading gives the most accurate number. Your rate per kWh is on your utility bill; include delivery charges for a realistic all-in price.
With the default inputs, the cost per month is $62.05. Change any value above to recalculate instantly.
How to use the electricity cost calculator
- 1Find the wattage on the appliance label, charger or manual (or measure it with a watt meter).
- 2Enter how many identical devices you want to price.
- 3Enter the hours per day and days per week the device runs.
- 4Enter your all-in electricity rate per kWh from a recent bill.
- 5Read the monthly and yearly cost, and use the chart to compare periods.
Formula and method
Power in watts is converted to kilowatts by dividing by 1,000, then multiplied by hours of use to get kilowatt-hours (kWh), the unit your utility bills in. A 1,500 W heater running for one hour uses 1.5 kWh.
Daily energy is scaled to a year by the number of days you actually use the device (days per week × 365 ÷ 7) and multiplied by your price per kWh. The monthly figure is the yearly cost divided by 12, so it reflects an average month rather than a 30- or 31-day month. The calculation assumes a constant draw at the rated wattage.
- W
- Power draw of one device in watts
- qty
- Number of identical devices
- h
- Hours of use per day
- rate
- Price per kilowatt-hour
Worked examples
1,500 W space heater, 8 hours a day
A 1,500 W heater uses 1.5 kWh per hour, or 12 kWh over an 8-hour day. Every day for a year that is 4,380 kWh, which at $0.17/kWh costs $744.60 — about $62.05 a month or $2.04 per day.
Gaming PC, 450 W, 4 hours on weekdays
At 450 W for 4 hours the PC uses 1.8 kWh per session, costing $0.36 at $0.20/kWh. Five days a week is about 260.7 days a year, or 469 kWh and roughly $94 a year.
Three 60 W ceiling fans running all day
Three 60 W fans draw 0.18 kW together, costing 2.7 cents an hour. Running around the clock that is 4.32 kWh a day, about 131 kWh a month and $236.52 a year at $0.15/kWh.
Frequently asked questions
How do I calculate the cost to run an appliance?+
Multiply the wattage by the hours used and divide by 1,000 to get kWh, then multiply by your electricity rate. For example, 1,000 W for 3 hours is 3 kWh; at $0.17/kWh that costs $0.51.
Where do I find an appliance’s wattage?+
Look for a label on the back or underside, the power adapter, or the manual. If only amps are listed, multiply amps by volts (usually 120 V in the US, 230 V in Europe). A plug-in watt meter measures real usage.
Why is my real cost lower than the calculator shows?+
Appliances with thermostats or compressors — fridges, heaters, air conditioners — cycle on and off, so they run at full power only part of the time. Enter the hours they actually run, or measure with a watt meter.
What is a typical electricity rate?+
Rates vary widely by location and plan. Recent US residential averages have been around 17–18 cents per kWh, while some states and many European countries pay 30 cents or more. Use the all-in rate from your own bill.
Which household devices cost the most to run?+
Heating and cooling equipment, electric water heaters, clothes dryers, pool pumps, hot tubs and EV charging usually dominate. Small electronics cost little individually but standby loads across many devices can add up.