Power Consumption How do we measure the electricity we use? This presentation came from Virginia Tech and has not been edited by the Georgia Curriculum Office.

Performance objective Students will be able to read an electric meter and determine the kilowatt hours used for a particular billing period.

Enabling objectives Given instruction in class and an electric meter, students will determine the kilowatt-hours used and estimate the electric bill for a particular billing period.

Interest Approach  Have you ever noticed how the meter reader comes to your house to read the meter?  Have your ever looked at an electrical meter?  What did it look like?  Did you ever wonder what was read?  What are actual and estimated readings.

The Electric Meter  An electric meter is usually installed by the power supplier at each service drop. It is used to measure and record the amount of kilowatt-hours used by a home or business for the month. Where is the meter at your house?

The Electric Meter  The meter is sealed inside a glass case and has a series of what appears to be clock faces geared together. Underneath the clock faces is a horizontally mounted wheel that turns whenever electricity is used.

The Electric Meter  The meter is read from right to left. As the first dial makes a complete revolution it causes the next one to the left to move one position. The same holds true for the relationship between the other dials. Always read the number the dial has just passed.

Read the Meter

Calculation  Simply record the reading at the beginning and end of the month, then subtract to find the number of kilowatt- hours used for the month.  Example Jan  Jan

Subtract the readings  Subtract to find the kilowatt-hours used  – = (X) kilowatt-hours used  856 Kilowatt-hours

Estimating the electric bill  If electricity is sold for an average cost of 7 cents per kilowatt-hour, we can estimate the electric bill for the month by multiplying the kilowatt- hours by the price per kilowatt-hour.  856 kilowatt-hours x $.07 = $59.92

Estimating the electric bill  Remember this is still an estimate, since the power company adds fuel factors and bills differently for the number of kilowatt hours used. This is, however, a good method for estimating.

What factors affect usage?  We do not use the same amount of electricity each month ordinarily. What factors would affect the amount used?

Factors that affect usage.  Seasonal changes in temperature cause greater consumption especially when we heat or cool with electricity.

Actual reading vs. Estimates  Sometimes the power supplier doesn’t read the meter every month. Instead they use previous records from years past to estimate the electricity used at a service drop. Over the course of several months readings will actually be taken to correct any discrepancy between estimated readings and actual ones.

Summary  Always read the meter from right to left and record the number the dial has just passed.  The difference between readings at the beginning and end of the month, multiplied by the cost per kilowatt- hour, can be used to estimate the electric bill.