Appliance Energy Calculator

About the Appliance Energy Calculator

Every household is full of appliances quietly using electricity, from the fridge that never switches off to the television waiting on standby for the remote. Some are obvious energy users, others are surprisingly cheap, and a few cost far more than people expect. Knowing which is which makes it much easier to cut a bill, choose a new appliance or decide whether it is worth replacing an old one.

This appliance energy calculator gives the yearly energy use, running cost and carbon emissions for common household appliances — a fridge- freezer, TV, computers, games console, kettle, microwave, air conditioner, heater, dehumidifier and light bulbs — using typical power and hours of use, or for any appliance with your own figures. It also counts standby power, the electricity used while an appliance is switched off but still plugged in.

How to Use the Appliance Energy Calculator

Choose the appliance. The list shows the power, daily hours and standby power assumed for each.

To use your own figures, choose custom and enter the power in use, the hours in use a day and the standby power.

Enter the number of appliances, your electricity price per kWh, and the carbon intensity of your electricity if you know it.

How Appliance Energy Is Worked Out

  in use       =  watts × hours in use ÷ 1,000              (kWh a day)
  standby      =  standby watts × (24 − hours in use) ÷ 1,000
  a day        =  (in use + standby) × number of appliances
  a year       =  a day × 365
  cost         =  kWh a year × price per kWh
  carbon       =  kWh a year × kg CO₂ per kWh

Step-by-Step Example

A TV: 100 watts for 4 hours a day, 1 watt on standby, electricity at 0.16 per kWh, 0.4 kg of CO₂ per kWh.

  In use:     100 × 4 ÷ 1,000          =  0.4 kWh a day
  Standby:    1 × 20 ÷ 1,000           =  0.02 kWh a day
  A year:     0.42 × 365               =  153.3 kWh
  Cost:       153.3 × 0.16             =  24.53 a year
  Standby:    7.3 kWh, 1.17 a year     (about 4.8% of the total)
  Carbon:     153.3 × 0.4              =  61.3 kg of CO₂

Typical Yearly Use and Cost

At 0.16 per kWh, using the typical figures in the calculator:

These assume daily use all year. Heaters and air conditioners are seasonal, so their real yearly figures depend on how many months you use them.

Standby Power

Many appliances draw a small amount of power when they appear to be off: TVs waiting for the remote, microwaves with clocks, games consoles in rest mode, chargers left in the socket. Modern devices usually use under 1 watt on standby, but older ones and some "instant-on" modes use 10 watts or more. Every watt left on all year uses 8.76 kWh. Across a whole home, standby can add up to several percent of an electricity bill. Switching devices off at the wall, or using a smart plug, removes it.

Reading Energy Labels

Many countries require energy labels on large appliances, showing an efficiency rating and an estimated yearly energy use in kWh. That figure is the most useful number on the label: multiply it by your electricity price to get the running cost. When choosing between two models, the difference in yearly kWh multiplied by the price, and by the years you expect to keep the appliance, shows how much the more efficient model saves over its life.

Carbon Emissions

The carbon footprint of an appliance depends on how the electricity is made. Grids powered largely by coal and gas produce 0.5 to 0.9 kilograms of CO₂ per kWh; grids with a lot of wind, solar, hydro and nuclear power produce under 0.2. The US average is around 0.4. Electricity suppliers and grid operators publish their figures, and some apps show the live carbon intensity, so you can run heavy appliances when the grid is cleanest.

When to Replace an Old Appliance

Old fridges and freezers are often the best candidates for replacement, because they run all day, every day. A fridge-freezer from the early 2000s can use 500 to 700 kWh a year, against around 300 for a modern efficient model. At 0.16 per kWh, saving 300 kWh a year is worth 48.00 a year, so a new appliance may repay a good part of its price over its life, especially if the old one needed replacing soon anyway. For appliances used only occasionally, such as a microwave or kettle, replacing a working model rarely saves enough to justify the cost.

Small Changes That Add Up

Boil only the water you need in the kettle. Keep the fridge at about 3 to 5 °C and the freezer at −18 °C, and defrost the freezer if ice builds up. Turn the TV and computer off rather than leaving them idle, set games consoles to a low-power standby mode, and let laptops sleep automatically. Use a dehumidifier or air conditioner with a timer or humidistat rather than running it all day.

Understanding Your Result

Running cost is the yearly cost.

Energy gives the kWh a day and a year.

Daily and monthly cost gives shorter periods.

Standby shows how much of the total is standby power.

Carbon estimates the yearly CO₂ emissions.

Assumed use confirms the power and hours used in the calculation.

When Should You Use This Calculator?

Choosing a new appliance and comparing running costs.

Deciding whether to replace an old fridge or heater.

Tracking down a high electricity bill.

Cutting standby waste around the home.

Estimating a household's carbon footprint.

Common Mistakes

Ignoring standby power.

Using the maximum wattage for appliances that cycle on and off.

Counting seasonal appliances as if used all year.

Forgetting the number of appliances, such as bulbs.

Comparing appliances on price alone without running costs.