1. Electrical Energy Use in the Home
In an electric meter in your home, the electrical energy is measured in kilowatt hours (kW x h).

2. 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 = W x S = J

3. 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.

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

5. 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 ($)

6. Appliances
Average power W
Monthly Energy Use kW x h
Approximate
Costs $
Air conditioner
750
7.20 – 43.30
Clothes Dryer
5000
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

7. 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 W x 1kW/1000w = 0.500kW
Cost = p x t x rate
Cost = 0.500kW x 24hrs x $0.08/ kW x $0.96

8. 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

9. 2. Calculate the cost of a 1. 5kW electric kettle that operates for 0
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

10. 3. Calculate the cost of a television that has a power rating of 0
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 = x (9h x 7) x $0.08/ kW x h = $7.64

11. 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