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Electric EnergyMeasurement, Units, and cost
Your Electric Bill
Cost to Operate Appliances
Topics
Part 1: Your Electric Bill What Electric Energy is How Electricity is Measured Reading your Electric Bill
Part 2: Cost to Operate Appliances Power – Energy - Cost Reading Appliance name plates Calculating the cost to operate
appliances
Key Terms
Voltage Current Resistance Load Power Energy Kilowatt Kilowatt - Hour
Part 1: Your Electric Bill
What is Electric Energy? Energy helps us do many things. Energy is defined as the ability to
do work. Electrical Energy is
Easily convertible to other forms Easily moveable from one area to
another Not easily stored
Units of Measure Ohm’s Law: V=IR Power Law: P=IV Voltage Current Resistance Time Rate of Energy Usage
Power Watts = Joule/s
Energy Used Kilowatt-hours
How Electricity is Measured
Read both sets of dials and calculate the usage per day.
(41615 – 40565) / 5 = 1050 kWH / 5 days = 210 kWH/day
Part 2: Cost to Operate Appliances
Power – Energy - Cost Energy consumed: E = P t
E =100 W bulb left on for 20 hours = 2 kWH
Cost to Operate: C = E RC = 2 kWH x $0.15 / kWH = $0.30
Reading Appliance Nameplates
Calculating the Cost to Operate an Appliance
Power consumed: P = I VA 120V appliance with 2 Amps of current uses 240 Watts of power.
Duty cycle: The total number of hours that the appliance is on during a
typical period of time (day, month, or year).2 hour/day = 2 x 365 = 739 hr/yr
It is sometimes shown as a percentage2 hour/day = 2 hour / 24 hours = 8%739 hour/yr = 739 / 8760 = 8%
Energy Consumed: E = P tE = 240 W x 2 Hr/day = 0.480 kWH/day
Cost to Operate: C = E RC = 0.480 kWH x $0.15/kWH = $0.072 each day
Annualized Cost$0.072 /day x 365 day/yr = $26 / yr