The Cost of Electricity and how the power companies charge us? Kilowatt hour, what is it?. All this questions are what we ask ourselves all the time when we are paying and paying for the cost of electricity. Here are some of the answers that we need to know. The wattage will be printed on the device or its label. To get kilowatt-hours, take the wattage and divide by 1000 to turn it into kilowatts, and then multiply by the number of hours you’re using the item. That’s exactly what the table below is for. If you’d rather not do the math then you can use a Free Cost of Electricity Calculator that you is very handy to use.
That same chart also has a list of the wattage for most household devices.
Before we see how much electricity costs, we have to understand how it’s measured. When you buy gas they charge you by the gallon. When you buy electricity they charge you by the kilowatt-hour (kWh).
When you use 1000 watts for 1 hour, that’s a kilowatt-hour.
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- For example:
If your device lists amps instead of watts, then just multiply the amps times the voltage to get the watts. For example: 2.5 amps x 120 volts = 300 watts (If you’re outside North America, your country probably uses 220 to 240 volts instead of 120.)
You can’t always trust the wattage on the label, because many devices don’t use the full listed wattage all the time. For example, the compressor in a refrigerator doesn’t run constantly, only sometimes, so you can’t go by the label for a fridge.
My calculator takes this into account by listing the average wattage for fridges. The most accurate way to find the average wattage of a device is to measure it with a watt-hour meter.
Exercise #1. Go get your electricity bill and see how many kilowatt hours you used last month. Also see if it lists how much you’re paying per kilowatt hour.
Exercise #2. Assume that the lights in your kitchen and living room together use 400 watts. How much does it cost if the lights are on 24 hours a day, for a whole month? How much per year? Assume 15¢/kWh. (see answer) • 400 watts x 24 hours/day x 30.5 days/month = 292,800 Total Watt-hours • 292,800 Wh / 1000 Wh = 293 kwh • 293 kWh x 15¢/kWh = $44/mo.; $528/yr.
Exercise #3. Assume your window AC uses 1440 watts. How much does it cost to run it continuously for a month? How much per year? Assume 15¢/kWh. (see answer) • 1440 watts x 24 hours/day x 30.5 days/monh = 1,054,080 Total Watt-hours • 1,054,080 Wh / 1000 Wh = 1,054 kWh • 1,054 kWh x 15¢/kWh = $158/mo.; $1986/yr.
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