Use this Formula to Calculate Your Appliances' Energy Use

# Use this Formula to Calculate Your Appliances' Energy Use

Taryn Williford
Sep 2, 2011

We talk a lot about trying to cut down our energy use, giving you vague suggestions to save power, like switching to a room air conditioning unit because central A/C uses "around 3.5 times" the energy. But figures like that depend exclusively on your habits at home. If you want to figure out how much wattage your specific appliances are burning, turn to this formula.

The U.S. Department of Energy offers up this formula for calculating your home energy use. It's straightforward, sure. And definitely something we could have figured out on our own. But since we're several years out of algebra class, it's awesome that somebody else has spelled it out:

You can use this formula to estimate an appliance's energy use:

(Wattage × Hours Used Per Day) ÷ 1000 = Daily Kilowatt-hour (kWh) consumption

1 kilowatt (kW) = 1,000 Watts

Multiply this by the number of days you use the appliance during the year for the annual consumption. You can then calculate the annual cost to run an appliance by multiplying the kWh per year by your local utility's rate per kWh consumed.

You can find your appliances' specific wattage from the appliance itself (check for a sticker or nameplate), its packaging, the manufacturer's website, or sometimes just by Googling the model number.

If you need some help, here's a list of the average wattage of most household appliances:

Aquarium = 50–1210 Watts
Coffee maker = 900–1200
Clothes washer = 350–500
Clothes dryer = 1800–5000
Dishwasher = 1200–2400 (using the drying feature greatly increases energy consumption)
Dehumidifier = 785
Electric blanket- Single/Double = 60 / 100
Fans
Ceiling = 65–175
Window = 55–250
Furnace = 750
Whole house = 240–750
Hair dryer = 1200–1875
Heater (portable) = 750–1500
Clothes iron = 1000–1800
Microwave oven = 750–1100
Personal computer
CPU - awake / asleep = 120 / 30 or less
Monitor - awake / asleep = 150 / 30 or less
Laptop = 50
Refrigerator (frost-free, 16 cubic feet) = 725
Televisions (color)
19" = 65–110
27" = 113
36" = 133
53"-61" Projection = 170
Flat screen = 120
Toaster = 800–1400
Toaster oven = 1225
VCR/DVD = 17–21 / 20–25
Vacuum cleaner = 1000–1440
Water heater (40 gallon) = 4500–5500
Water pump (deep well) = 250–1100
Water bed (with heater, no cover) = 120–380

(Images: Flickr member dailyinvention licensed for use under Creative Commons, Flickr member Reinos licensed for use under Creative Commons)