How to calculate electricity cost per kWh

6 October 2026 · Calcosmo editorial team

To work out what an appliance costs to run, convert its power to energy with watts × hours ÷ 1,000 = kWh, then multiply by your price per kWh. A 100-watt TV used 5 hours a day uses 183 kWh a year; at $0.17 per kWh that is $31 a year. Run your own numbers with the kWh calculator.

Step 1: find the wattage

The power rating in watts (W) is on the label or rating plate, usually on the back or bottom of the appliance, or in the manual. If it shows a range such as 1,800–2,200 W, use the middle. For appliances that cycle on and off, such as fridges, washing machines and laptops, the label shows the maximum. For those, the annual kWh figure on an energy label is a better guide.

Step 2: convert watts to kWh

A kilowatt-hour (kWh) is 1,000 watts for one hour.

kWh = watts × hours ÷ 1,000

A 2,000 W kettle used for 15 minutes a day: 2,000 × 0.25 ÷ 1,000 = 0.5 kWh per day, or 182.5 kWh a year.

Step 3: multiply by your price

Your price per kWh is on your electricity bill, usually as the "energy charge" or "unit rate". Use the rate including taxes. Standing charges and fixed fees are paid regardless of use, so leave them out when costing a single appliance.

Prices vary widely by country, supplier and tariff. The examples below use $0.17 per kWh as an illustration; replace it with your own rate. The calculator starts with 0.20 as a placeholder, so always enter the rate from your own bill.

Examples

At $0.17 per kWh, 365 days a year:

Small devices that are always on add up. A PC that never sleeps costs far more than a kettle used every day.

Cost per hour

Sometimes you just want the hourly cost: kW × price. A 1.5 kW space heater at $0.17 costs 1.5 × 0.17 = $0.26 per hour. A 2.5 kW tumble dryer cycle of an hour costs about $0.43.

Measure instead of estimate

A plug-in energy monitor measures the actual consumption, including standby use and appliances whose power varies. Leave it on a fridge for at least 24 hours. With a smart meter, you can also watch your household usage jump when you switch something on.

Ways to cut the cost

• Switch devices with standby power fully off with a switched power strip.
• Boil only the water you need.
• Replace halogen and incandescent bulbs with LEDs, which use around 80 to 90% less power.
• When replacing a fridge, washing machine or dryer, compare the annual kWh on the energy label; a difference of a few hundred kWh adds up over ten years.