Kwh Cost Calculator

Find out what any appliance costs to run. Enter its power in watts, how many hours a day you use it and your electricity rate per kWh, and see the cost per hour, day, month and year. Add several devices to see which ones drive your bill.

How electricity cost is calculated

Your utility charges for energy in kilowatt-hours (kWh). A kilowatt-hour is the energy used by a 1,000-watt device running for one hour. To find the cost of running an appliance:

1. Convert watts to kilowatts: watts ÷ 1,000.
2. Multiply by hours of use to get kWh.
3. Multiply kWh by your price per kWh.

A 1,500-watt space heater running for 3 hours uses 1.5 × 3 = 4.5 kWh. At $0.17 per kWh, that is about $0.77 a day, or about $23 a month if used every day.

Finding your appliance's wattage

• Look for a label on the back or bottom of the appliance, or on its power adapter: it may list watts (W), or volts (V) and amps (A) — multiply volts × amps for approximate watts.
• Check the manual or the manufacturer's website.
• For refrigerators, water heaters and dishwashers, the yellow EnergyGuide label in the US gives estimated yearly kWh directly.
• A plug-in energy monitor measures real consumption over days, which is the most accurate for devices that cycle on and off.

Duty cycle: appliances that switch on and off

Many appliances do not run at full power the whole time. A refrigerator's compressor cycles on and off; a thermostat-controlled heater or air conditioner runs harder on extreme days; a dryer's heater cycles as it reaches temperature. The duty-cycle field lets you account for this: if a 150-watt fridge compressor runs about a third of the time, enter 33% with 24 hours a day. When in doubt, a plug-in meter or the EnergyGuide yearly kWh figure gives the most realistic number.

What is your electricity rate?

Your bill shows the price per kWh, often split into supply (generation) and delivery charges plus taxes. For a simple estimate, divide the total of your bill's energy-related charges by the kWh used that month. Rates vary widely by location and season; many US households pay somewhere between about 12 and 30 cents per kWh. If you have time-of-use pricing, use the rate for the hours when the appliance actually runs.

Typical appliance wattages

Worked example: which device drives the bill?

The multi-appliance table starts with a refrigerator averaging 150 W for 8 hours of compressor time a day (36 kWh a month), a TV at 100 W for 5 hours (15 kWh), and an electric water heater at 4,000 W for 3 hours (360 kWh). At $0.17 per kWh, the water heater costs about $61 a month — around 88% of the total — while the TV costs about $2.55. Heating and cooling appliances almost always dominate, which is where savings efforts pay off most.

Ways to cut the cost

• Lower the water heater temperature to around 120 °F (49 °C) and fix dripping hot taps.
• Use heating and cooling setbacks when away or asleep.
• Air-dry laundry or run full dryer loads with clean lint filters.
• Replace remaining incandescent bulbs with LEDs.
• Unplug or switch off devices with high standby use, such as older set-top boxes and chargers.
• Shift flexible loads such as dishwashers and EV charging to off-peak hours if you have time-of-use rates.

Standby power

Many electronics draw a small amount of power even when switched off or idle — often called standby, vampire or phantom load. Individually it may be only a few watts, but across a household of devices it can add up to a noticeable share of consumption. A device drawing 5 W continuously uses about 44 kWh a year. Smart power strips that cut power to peripherals when the main device is off, and switching off at the wall, reduce this waste.