Estimating Household Appliance Energy Use

If you 're trying to adjudicate whether to invest in a more energy-efficient appliance or you'd like to establish your electricity loads, you may want to estimate appliance energy consumption. So, you can use the formula below before you buy appliances. 

  

Estimating Energy Consumption Formula

This formula can be used 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 breeding the kWh each year by your local utility's rate per kWh spent.

Note : To estimate the number of hours that a refrigerator actually operates at its maximum wattage, divide the total time the refrigerator is plugged in by three. Refrigerators, although turned "on" all the time, actually cycle on and off pro re nata to maintain interior temperaturs.

Examples:

Portable fan:
(200 Watts × 4 hours/day × 120 days/year)  ÷  1000
= 96 kWh × 8.5 cents/kWh
= $8.16/year
PC and Monitor:
(120 + 150 Watts × 4 hours/day × 365 days/year)  ÷  1000
= 394 kWh × 8.5 cents/kWh
= $33.51/year

Electrical Power (Wattage)
You can usually find the electrical power of most appliances stomped on the bottom or back of the appliance, or on its nameplate. The electrical power listed is the maximum power drawn by the appliance. Since many appliances have a range of settings (for instance, the volume on a radio), the actual amount of power consumed depends on the setting used at any in one case.

f the electrical power 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 drier 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 ammeteran electrician's tool that clinches around one of the two wires on the applianceto 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.

When quantifying the current drawn by a motor, note that the meter will show about threefold more current in the first second that the motor starts than when it is running smoothly.

A lot of appliances continue to draw a small amount of power when they are switched "off." These "phantom loads" come in most appliances that use electricity, such as Videocassettes recorder, televisions, stereos, computers, and kitchen appliance. Most phantom loads will increase the appliance's energy consumption a couple of watt hours. 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. 

Distinctive Wattages of Various Appliances

Here are some examples of the range of nameplate electricals power for various home appliance :

• 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
• 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
• Radio (stereo) = 70–400
• 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