Electricity Cost Calculator

Please fill in the required fields with values greater than 0.
–kWh per day
–cost per day
–cost per month (30 days)
–cost per year

Estimate only. Check your electricity bill for your exact rate. Power use varies with how an appliance is used.

How to use this calculator

Enter the appliance power in watts, the hours it runs each day, the number of appliances and your electricity rate. Press Calculate to see the energy use and the daily, monthly and yearly cost.

The formula

kWh per day = watts × hours × number of appliances ÷ 1,000
Cost = kWh × rate per kWh

Example: A 1,500 W heater used 2 hours a day uses 3 kWh a day. At $0.17 per kWh that costs $0.51 a day, $15.30 a month and $186.15 a year.

What affects what an appliance costs to run

This calculator estimates the cost of running an appliance from its wattage, the hours you use it and your electricity rate. The daily, monthly and yearly figures help you see which devices are worth worrying about and which barely register on your bill.

What the result means in practice

The estimate assumes the appliance draws its full rated wattage the whole time it is on. That is close to true for simple heaters, hair dryers and incandescent bulbs. Many other appliances, such as refrigerators, air conditioners and dehumidifiers, cycle on and off. Their real use is often lower than the label suggests. Treat the result as an upper estimate for those devices.

Real-world examples

A 300 W gaming computer used 4 hours a day uses 1.2 kWh per day. At $0.17 per kWh, that is about $0.20 per day, $6.12 per month and $74.46 per year. A 1,000 W window air conditioner running 8 hours a day uses 8 kWh. At the same rate, that is $1.36 per day, or about $40.80 per month during cooling season.

Main factors that change the cost

  • Wattage: Devices that make heat, such as space heaters, ovens and dryers, use the most power.
  • Hours of use: A low-watt device left on all day can cost more than a high-watt one used for minutes.
  • Settings: Thermostat setpoints, eco modes and fan speed change actual draw.
  • Your rate: Rates vary by utility, plan and sometimes time of day.

Tips and common mistakes

  • Do not confuse watts with watt-hours. Watts are the rate of use, while kWh is the total energy.
  • Check the label for the real wattage. If it lists amps, multiply by 120 volts for most US outlets.
  • Count standby power. TVs, game consoles and chargers can draw a few watts all day.
  • For the most accurate number, use a plug-in energy meter for a week and divide by 7.

Using the result to save money

Run the calculator for your largest loads first, such as heating, cooling, water heating and laundry. These usually matter far more than phone chargers or lamps. When shopping for a new appliance, compare the yearly energy cost on the label along with the price, since a cheaper model can cost more to run over its life.

Frequently asked questions

How do I calculate the cost of running an appliance?
Multiply the watts by the hours used and divide by 1,000 to get kWh. Multiply the kWh by your electricity rate.
Where do I find the wattage of an appliance?
Check the label or the manual. If it only shows amps and volts, multiply them to get watts.
What is a kWh?
A kilowatt-hour is the energy used by 1,000 watts running for one hour. It is the unit on your electricity bill.
What is my electricity rate?
Look at your bill for the price per kWh, and divide the total charges by the kWh used if only the total is shown.
Which appliances use the most electricity?
Heating and cooling, water heaters, dryers and ovens use the most, followed by refrigerators and lighting.
How much does it cost to run a space heater?
Most portable electric space heaters draw about 1,500 W on high. Running one for 5 hours a day uses 7.5 kWh. At $0.17 per kWh, that is about $1.28 per day, or roughly $38 per month. Using the low setting, a thermostat, or heating only the room you are in lowers the cost.
What is phantom or standby power?
Phantom power is electricity used by devices that are turned off but still plugged in. TVs, cable boxes, game consoles, chargers and anything with a clock or remote can draw a few watts all the time. Each one is small, but together they add up over a year. A smart power strip can cut them off automatically.
How do I convert amps to watts?
Multiply amps by volts. Most standard US outlets supply about 120 volts, so a device rated at 10 amps draws about 1,200 watts. Large appliances like dryers and ranges often use 240 volts, so a 20-amp dryer circuit can carry about 4,800 watts. Use the volts listed on the appliance label.