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Energy and Safety

Calculating Energy Use

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Online Home Energy Analysis

Calculating energy use based on a description of your own house and appliances can help identify the best opportunities for energy savings.

For a quick and easy way to find out how your home energy use compares with the average, try the ENERGY STAR Home Energy Yardstick. You will need to enter some common information about your home such as age, square footage, number of occupants and energy bill totals for a consecutive 12-month period. You can access your bills online by going to My Account.

For a more detailed analysis, use the U.S. Department of Energy's Home Energy Saver. Users can begin the process by simply entering their zip code, and in turn receive an instant initial estimate. By providing more detailed information about your home, you can receive increasingly customized results along with energy-saving upgrade recommendations.

Energy Use of Some Typical Home Appliances

Knowing how much electricity each of your appliances uses will also give you a clearer picture of where your energy dollar is going. Powered with this knowledge, you can use energy more efficiently and have greater control over your energy budget.

If you want an estimate of how much electricity your home appliances consume, refer to the Household Appliances list below. If you want a more exact estimate, you can generally find the wattage stamped on the bottom or back of the appliance, or on its "nameplate." The wattage listed is the maximum power drawn by the appliance. Since many appliances have a range of settings (for example, the volume on a radio), the actual amount of power consumed depends on the setting used at any one time.

Use the following formula to estimate the amount of energy a specific appliance consumes:

Wattage x Hours Used Per Day = 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 the cost per kWh consumed. Refer to your most recent energy bill for the latest kilowatt-hour rate.

Examples:
Appliance
Watts x Hours per Day x Days per Year ÷ Convert to kWh x kWh Rate = Cost per Year
Window Fan 200 x 4 x 120 ÷ 1,000 x .14 = $13.44
Radio 400 x 4 x 365 ÷ 1,000 x .14 = $81.76
Household Appliances:

Aquarium = 50-1210 Watts
Clock radio = 10
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
Ceiling fan = 65-175
Window fan = 55-250
Furnace = 750
Whole house fan = 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
Radio (stereo) = 400
Refrigerator (frost-free, 16 cubic feet) = 725
Television (color):
19" = 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 (w/ heater, no cover) = 120-380

Refrigerators, although turned "on" all the time, actually cycle on and off at a rate that depends on a number of factors. These factors include how well it is insulated, room temperature, freezer temperature, how often the door is opened, if the coils are clean, if it is defrosted regularly, and the condition of the door seals. To get an approximate figure for the number of hours that a refrigerator actually operates at its maximum wattage, divide the total time the refrigerator is plugged in by three.

If the wattage is not listed on the appliance, you can still estimate it by finding the current draw (in amperes) and multiplying that by the voltage used by the appliance. Most appliances in the United States use 120 volts. Larger appliances, such as clothes dryers and electric cooktops, use 240 volts. The amperes might be stamped on the unit in place of the wattage. If not, find a clamp-on ammeter—an electrician's tool that clamps around one of the two wires on the appliance — to measure the current flowing through it. You can obtain this type of ammeter in stores that sell electrical and electronic equipment. Take a reading while the device is running; this is the actual amount of current being used at that instant.

Note: When measuring the current drawn by a motor, in the first second that the motor starts, the meter will show about three times the current than when it is running smoothly.

Also note that many appliances continue to draw a small amount of power when they are switched "off." These "phantom loads" occur in most appliances that use electricity, such as VCRs, televisions, stereos, computers, and kitchen appliances. Most phantom loads will increase the appliance's energy consumption a few watts per hour. These loads can be avoided by unplugging the appliance or using a power strip and using the switch on the power strip to cut all power to the appliance.

Source: U.S. Department of Energy