Electrical Energy Use in the Home

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Electrical Energy Use in the Home

• In an electric meter in your home, the electrical
  energy is measured in kilowatt hours (kW x h).

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• There are 3 600 000J in one kW x h, therefore it
  is much more practical to use kilowatt hours.
• 1 kW x h 1000W x 3600s 3 600 000 W x S 3 6
  00 000J

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• A kilowatt hour refers to 1000 watts being used
  over an hour, therefore a 100W bulb would have to
  be on for 10 hours to equal 1 kilowatt hour.

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• The electrical meter in your home records the
  total amount of electricity used in your home.

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• In order to calculate the cost of electrical
  energy used in your home you can use the
  following formula
• Cost Power (kW) x time (h) x rate ()

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Appliances Average power W Monthly Energy Use kW x h Approximate Costs
Air conditioner 750 90 - 540 7.20 43.30
Clothes Dryer 5000 50 - 150 4.01 12.03
Television 80 5 - 15 0.41 1.20
Lighting 60W bulb 60 5 - 30 0.40 2.41
Microwave Oven 1000 5 - 20 1.40 1.60
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Example A

• Calculate the cost of the electricity needed to
  operate a refrigerator/freezer (500W) for a day
  if the rate charged for electricity is 0.08/ kW
  x h
• First convert watts to kW 500W x 1kW/1000w
  0.500kW
• Cost p x t x rate
• Cost 0.500kW x 24hrs x 0.08/ kW x 0.96

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• Calculate the cost of running a coffee maker that
  has a power rating of 0.900kW and operates for 17
  hours. (rate is 0.08/ kW x h)
• Cost 0.900kw x 17h x 0.08/ kW x h
  1.22

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• 2. Calculate the cost of a 1.5kW electric kettle
  that operates for 0.80h per day for two weeks.
• Cost 1.5kw x (0.8h x 14) x 0.08/ kW x
  1.34

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• 3. Calculate the cost of a television that has a
  power rating of 0.120kW uses in one week if it
  operates for 9 hours every day.
• Cost 0.120 x (9h x 7) x 0.08/ kW x h
  7.64

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• 4. Calculate the cost of a computer monitor and
  printer if the monthly energy use is 25 kW x h at
  a rate of 0.08/ kW x h.
• Cost 25 kW x h x 0.08/ kW x h 2.00