Working out what an appliance costs to run

Knowing what each appliance and gadget uses shows you where the electricity money goes.

Power is measured in watts, and 1,000 watts is a kilowatt. What you pay for is energy used over time, measured in kilowatt-hours: one kilowatt used for one hour. Your electric bill charges a rate for each kilowatt-hour, so an appliance's wattage and the hours it runs give you what it costs.

What you need

• The appliance's wattage
• A rough idea of how many hours a day it runs
• Your electricity bill, for the rate per kilowatt-hour

Steps

1. 1

   Find the wattage

   Look on the bottom or back of the appliance for its label. The owner's manual or the maker's website may list it too.

   5 min

2. 2

   Estimate the hours a day

   Use what you know, such as 4 hours of television an evening, or keep a log for a few days.

   5 min

3. 3

   Work out the daily kilowatt-hours

   Multiply the wattage by the hours a day, then divide by 1,000.

   3 min

4. 4

   Work out the yearly kilowatt-hours

   Multiply the daily figure by the number of days a year the appliance is used.

   2 min

5. 5

   Work out the yearly cost

   Multiply the yearly kilowatt-hours by the rate per kilowatt-hour on your electricity bill.

   5 min

A worked example

An electric kettle labeled 1,500 watts runs about an hour a day in total, almost every day.

• Daily: 1,500 × 1 ÷ 1,000 = 1.5 kWh
• Yearly: 1.5 × 365 = 547.5 kWh
• Cost at 11 cents per kWh: 547.5 × $0.11 = about $60 a year

A 40-watt light bulb left on for five hours uses 200 watt-hours, or 0.2 kWh. At the same rate, that's about 2 cents.

The EnergyGuide label

The yellow EnergyGuide label on many home appliances shows the model's yearly energy use and running cost. It also shows how that compares with similar models. The appliances that carry one include refrigerators, freezers, dishwashers, clothes washers, water heaters, furnaces, heat pumps, air conditioners, ceiling fans and televisions. If you can't see it, look inside the appliance, or check the seller's or the maker's website.

The operating cost on the label is an estimate, based on typical use and a national average price for energy. What you pay depends on how you use the appliance and on your local rate, which is why your own numbers are worth working out.

Two price tags

An appliance has two costs: the price you pay for it, and the electricity it uses over its life. You'll pay for that electricity every month for 10 to 20 years, depending on the appliance. A model that costs more to buy but uses less can save money on your bills over time, and the yearly figures make the comparison.

Your meter

Your utility's meter, usually outside where the power line meets the house, measures what the whole home uses. Many utilities now use smart meters, which send usage data in real time, and some can track the use of a single device. Check whether your utility shows that data online.

Power drawn while it's off

Many electronics keep drawing power when they're switched off, which can add 5% to 10% to a monthly utility bill. An advanced power strip, with a timer, an activity monitor or a remote, stops that draw when the devices aren't in use. Unplug battery chargers once the batteries are full or when nothing is charging.