1. Paying for Electricity

2. Measuring Electrical Energy The electrical energy that you use at home is measured in kilowatt hours (kW  h) The images above all represent 1 kWh of energy use. (A) A 100 W bulb on for 10 hours (B) Ironing for 1 hour (C) Jogging for 1 hour (D) Having a hot shower for 3 minutes

3. Electric Meters Electric meters, such as the one shown below, continuously measure the amount of electrical energy that is used in a building

4. Smart Meters and Time-of-Use Prices Modern electrical meters, called smart meters, allow power companies to charge different prices for electricity, depending on the time of day it is used Smart meters measure the amount of energy that is used every hour

5. Time-of-Use Pricing

6. The Cost of Electricity Just as you pay so much money per kilogram, when you buy fruits and vegetables, you pay a certain amount of cents per kilowatt-hour when you use electricity Formula: Cost = Energy (kW  h) X price

7. Sample Problem #1 Calculate the cost of the electricity needed to operate a refrigerator for one month, if it uses 75 kW  h of energy. The price of electricity is $0.089 / kW  h. G: E = 75 kW  h price = $ 0.089/kW  h R: Cost A: Cost = E X price S:cost = 75 kW  h X $ 0.089/kW  h cost = $ 6.68 P:It costs $ 6.68 to operate a refrigerator for one month

8. Sample Problem #2 You run your 1200 W dishwasher every night before you go to sleep for 30 min each time. Calculate the total weekly cost if your price is $0.07 per kW  h. G: P = 1200 W = 1.2 kWt = 0.5 h (30 min) X 7 = 3.5 h price = $ 0.07/kW  h R: Cost Find E first A: E = P X t Cost = E X price S:E = 1.2 kW X 3.5 h E = 4.2 kW  h Cost = 4.2 kW  h X $0.07 / kW  h Cost = $0.29 P:It costs 29 cents to run the dishwasher for one week.

9. Homework “The Price of Energy” handout