Every renewable energy project has to start with analyzing your current energy consumption. For instance in a residential project you will want to start with doing an energy audit, recording the energy consumption of each appliance in your home.

This will help you to determine your energy loads and maybe even pinpoint a few appliances that could be replaced with a unit that is more efficient.

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 in kWh per year.

If you cannot find the wattage of your specific appliance you can estimate the current draw in amperes (amps) by either seeing if the amps are marked on the unit instead of the watts. You can then multiply the amps times the volts (most small appliances are 120v) to determine the watts.

Estimating the Annual Energy Cost

Multiply the annual consumption in kWh per year (that you calculated above) by your local utility's rate per kWh consumed to calculate the annual cost to run an appliance.

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 as needed to maintain interior temperatures.
Examples:

  Window fan:
(200 Watts × 4 hours/day × 120 days/year) ÷ 1000
= 96 kWh × 11 cents/kWh
= $10.56/year

  Personal Computer and Monitor:
[(120 Watts + 150 Watts) × 4 hours/day × 365 days/year] ÷ 1000
= 394 kWh × 11 cents/kWh
= $43.34/year

 

graph appliance-electricity

This chart shows how much energy a typical appliance uses per year and its corresponding cost based on national averages. For example, a refrigerator/freezer uses almost five times the electricity the average television uses. Courtesy of Energy.gov

 

Following are some examples of wattages for various 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
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

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