# How quickly does a 1kW appliance use energy?

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Terrible with math and I barely understand the concepts but if my fridge is a 1kw fridge, how long of running it at its “maximum” would it take to use 8700kj(average adult recommendation)

Looking for the math to be explained too please.

In: Other A 1 kW appliance uses 1kWh per hour. Converting 8700 kJ to kWh gives 2.4166667 kWh. Divide kWh by kW hives 2.41 hours or just under 2 hours 25 minutes. A kilojoules is one kilowatt per second. I don’t know where the 8790 KJ number you cited comes from, but it’s enough to run the refrigerator for 8.7 seconds.

8700 KJ / 1000 W = 8.7 seconds So two different answers? The 8700kj number came from the average persons daily intake. W = J/s. kW=1000W=1000J/s=1kJ/s. So 8700kJ takes 8700s.

W is power, the speed to generate or consume energy. a kilowatt would be whatever your voltage maths out to, to equal 1000 watts. so U.S. would be 120 volts to 8.33~ amps, I’m sure the 60 cycles per second factors in as well but I’m too science-illiterate to get into those details.

looking up the kilojoule conversion process, its kilojoules = watts × seconds / 1000 so if the fridge were converted into a formula as if it was running constantly, not sensing when to turn off and be consistent, that’ll be 86,400 seconds for a day and at 1 kwh, a whole day would be 86,400 kJ so 2.4 hours to be 8640, the power rating for the fridge probably isn’t magical but it is reasonably accurate for its rating so a 1 kw fridge would take around that long, possibly slightly longer as the rating is averaged over long periods of time with reasonable use. kW = Kilowatt

Kilo = 1000
Watt = 1 Joule per second

So 1 kW means “1000 joules per second” or 1 kJ per second.

Therefore it would take 8700 seconds to use 8700 kJ.