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