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Calculating Cost to Run Electrical Appliances. First, find the UL tag on the appliance. If power rating is given, move on to next step. If not, you must calculate the electrical power of the appliance. POWER = CURRENT X VOLTAGE P = IV (w) = (a)(V).
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Calculating Cost to Run Electrical Appliances • First, find the UL tag on the appliance. • If power rating is given, move on to next step. If not, you must calculate the electrical power of the appliance. • POWER = CURRENT X VOLTAGE P = IV (w) = (a)(V) Remember: Power is the rate at which work is done. A 100w light bulb converts electricity into light faster than a 60w light bulb. Therefore, it gives off more light!
Calculating Cost… con’t • Calculate the amount of electrical energy the appliance uses in a given period of time. • E = Pt (kWh) = (kW)(h) E = electrical energy P = electrical power T = time
Calculating Cost… con’t • Use the cost per kilowatt hour, to determine the cost to use the electrical appliance. Simply multiply cost per kWh by the number of kWh used by the appliance. • In Frederick, the cost is about 9 cents per kilowatt hour.
Sample Problem • How much does it cost to run the digital clock in my room for 24 hours? • The UL tag reads 8w (0.008kW) E = Pt E = 0.008kW x 24h E = 0.192kWh • 0.192kWh x 9cents / kWh = 1.728 cents
Sample Problem • What does it cost to make a batch of french fries in my deep fat fryer if they must cook for 7 minutes? • The UL tag reads: 12.5a, 120V • First, I must calculate its power rating. P = IV P = 12.5a x 120V I = 12.5a V = 120V P = 1500w
Next, Use the Power to calculate the Electrical Energy used. E = Pt P = 1500W = 1.5kW T = 7min = 0.12h E = 1.5kW x 0.12h E = 0.18kWh Finally, use the electrical energy to calculate the cost. 0.18kWh x 9c / kWh 1.62 cents to make a batch of fries.