3. Find its operating cost.
To Find Wattage:
Watts, you know, are the measure of electrical power. They are the product of voltage (pressure) times amperes (rate of flow). Volts times Amps equals Watts. The nameplate on the appliance will give the voltage required for proper operation as well as either amperage or watts. If it gives wattage, you have the information you want. Otherwise you must multiply volts times amps to get the wattage. When voltage is given as 110-120, use 120 as your voltage. 120 volts is nominal today.
How Much Will You Use?
Now that you know the wattage of the appliance, multiply this figure by number of hours the equipment operates in one day. Divide this by 1000 to get the kwh. Now multiply the result by the number of days the appliance is used each month. This tells you the number of kwh used by the appliance during the month.
Example No. 1
Yard Light: 300-watt lamp
Amount of use: 3 hours per night.
Multiply lamp wattage times hours of use per night to get watt-hours per night.
300 times 3 = 900 watt-hours per night.
Divide watt-hours by 1000 to get kwh per night.
900 divided by 1000 = .9 kwh per night.
Multiply kwh per night times 30 to get kwh per month.
.9 times 30 = 27 kwh per month.
If the yard light is used 3 hours per night, it consumes 27 kwh per month.
Example No. 2
Coffee Maker: 120 volts, 550 watts (from nameplate)
Amount of use: 1/2 hour per day.
Multiply wattage of coffee maker times hours of use per day to get watt-hours per day.
550 times 1/2 hour = 275 watt-hours per day.
Divide watt-hours by 1000 to get kwh per day.
275 divided by 1000 = .275 kwh per day.
Multiply kwh per day times 30 to get kwh per month.
.275 times 30 = 7.250 kwh per month.
If the coffee maker is used l/2 hour daily, it consumes 7.25 kwh per month.
Calculate Operating Cost Per Month