Calculating POWER and Electrical COST
ELECTRICAL POWER
Rate at which energy is consumed or produced Changed into other forms of energy
Measured in WATTS (W)
Calculations
Formula is P=IV Power=Current x Voltage
P
V I
Units:Power: wattsVoltage: voltsCurrent: amps
Electrical Energy
Depends on POWER (kW) and TIME (h) Units are kWh
The amount of electrical energy used in a home depends on the power of the electrical devices in the house and the length of time that those devices are on
Calculating Electrical Energy and Cost
Example: A coffee pot operates on 2 amperes of current on a 110-volt circuit for 3 hours. Calculate the total kWh used.
Step 1: Determine Power (P=VI) P = 110 Volts x 2 amps P= 220 watts
Step 2: convert watts to kilowatts 220 watts/1000 = 0.22 kW
Step 3: Multiply by the hours given in the problem 0.22 kW x 3 hrs = 0.66 kWh
Calculating Electrical Energy and Cost
What is the cost of using the coffee pot if the cost of energy is $0.15 per kWh?
Step 1: Multiply the kWh by the cost 0.66 kWh x 0.15 = $0.099
Appliance found Power used
(kW) Average time on a day (h)
Energy Used (kWh)
Cost per kWh ($)
Cost of running the appliance
($)
Ex. Blender .375 1 hour .375 0.1244 .04665
Total cost to run the room for one day
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