|---------------------------------------------| | | |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_ Now that you know the number of kilowatt hours an appliance uses, go to your rate schedule and your electric bill to see what the average kwh costs. Find the average cost of 1 kwh by dividing the amount of your bill by the total number of kwh used in a month. _Example_: 410 kwh used. $14.35 total monthly bill Average cost per kwh equals $14.35 divided by 410 kwh-3-1/2 cents per kwh. Therefore, the cost of operating the coffee maker for a month would be 3-1/2 cents times 7.25 kwh--25.4 or 25 cents. Cost of operating the yard light would have been 94.5 or 95 cents a month. (a) 6357 (b) 1963 (c) 8996 Correct answers to the meter readings shown on the preceding page. Adding Low Cost Helpers You can see, by looking at your rate schedule, that the average cost per kwh gets lower as you use more electricity. To find the cost of operating additional electrical equipment, the cost per kilowatt hour is found from the last "step" in the bill--the lowest cost per kwh of the electricity you're now using. Sometimes power suppliers give special rates for such equipment as electric water heaters. WHAT TO DO: Find the Cost of Operating Electrical Equipment Make and fill in the blanks of a chart showing the electrical equipment you have and the operating costs per month.