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