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#1
02-13-2006, 08:58 AM
 markotah Guest Posts: n/a
kWh / KW ????

I see on my bill I used 703KWH last month. My water heater has a 4500 watt (4.5KW) element in it. If I ran the unit continually for 1 hour how would I calculate the KWH?
Thanks,
Mark
#2
02-14-2006, 10:51 PM
 Robert Fogt Administrator Join Date: Dec 2005 Location: Seattle, WA Posts: 3,467 Rep Power: 13
Re: kWh / KW ????

As its name implies, kilowatt hours is indeed kilowatts * hours.

4.5 kilowatts * 1 hour = 4.5 kWh
#3
05-16-2007, 02:15 PM
 Unregistered Guest Posts: n/a
Re: kWh / KW ????

thx for helping with my energy econ homework
#4
07-29-2007, 11:37 PM
 want_a_pie Guest Posts: n/a
Re: kWh / KW ????

Thanks for helping me with my homework too =D
#5
10-11-2007, 11:48 AM
 Unregistered Guest Posts: n/a
Re: kWh / KW ????

thanks for doing my homework
#6
11-28-2007, 10:30 AM
 Unregistered Guest Posts: n/a
Re: kWh / KW ????

that ******* is wrong! i failed my test because of him!!!
#7
11-28-2007, 02:50 PM
 gubment_cheez Ultimate Supreme Bacon Cheese Member Join Date: Jan 2007 Location: Sac-o-Tomato, Cowafornia Posts: 354 Rep Power: 8
Re: kWh / KW ????

Quote:
 Originally Posted by Unregistered that ******* is wrong! i failed my test because of him!!!
no, Robert's answer is not wrong. kWh is KiloWatts Per 1 Hour. if a water heater had a 4.5 kW heating element, that ran for 1 hour (60 minutes, or 3600 seconds) --which is exactly what the question asked-- it would consume 4.5 kWh of power.
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#8
12-04-2007, 07:13 PM
 Pizza_Pi (Visitor) Guest Posts: n/a
Re: kWh / KW ????

kilowatt-hour (kWh) is a unit of Power. 1 kilowatt-hour means that it will use (or transfer) one kilowatt every hour. One kilowatt is the power of one thousand joules (J) per second (s). the h in kWh basically signifies just the alternative time unit used. It is used because it often provides results that can be explained in whole numbers easily with out common household appliances.
If you really want to know what the conversion for kWh to kW...
1 kWh = 0.000277777...kW
1 kW = 3600 kWh
#9
12-04-2007, 07:16 PM
 Unregistered Guest Posts: n/a
Re: kWh / KW ????

The conversion:
1 kWh = 0.00027777... kW
1 kW = 3600 kWh
1 kW = 1000 J / s

So, the answer would be 4.5 kW = 16200 kWh, or 16.2 mWh (megawatt-hours)
#10
12-04-2007, 07:25 PM
 Pizza_Pi Guest Posts: n/a
Re: kWh / KW ????

1 kW = 1 kW consistent for 1 hour, or 1 kWh
1 kW = 1000 J / s = 1 kJ / s
1 kWh = 1000 J / h = 3.6 kJ / h
kW (kilowatts), kWh (kilowatt-hours), J (Joules), s (seconds), h (hours), kJ (kilojoules), mJ (megajoules)
But if you ant to find how much power was consumed in an hour, then you multiply 1 kWh times 3600. You can look above to find conversions to Joules per second, and, including the units, you find that the two time units cancel out each other:
kWh / kW = (1000 J / h) / (1000 J / s)
= (3600000 J / s) / (1000 J / s)
= (3600000 J / s) * (s / 1000 J)
= 3600

Just some prefixes for units if you ever want to know.
(f) fempto = 0.000000000000001
(p) pico = 0.000000000001
(n) nano = 0.000000001
(micro symbol) micro = 0.000001
(m) milli = 0.001
(k) kilo = 1,000
(M) mega = 1,000,000
(G) giga = 1,000,000,000
(G) tera = 1,000,000,000,000
(P) peta = 1,000,000,000,000,000

If anything is wrong, tell me now and prove it. I always want to be right.

Oh, and Mark, the heater used 4.5 kWh, and it will consume 108 kWh daily if you leave it on 24/7.

Last edited by Pizza_Pi; 12-04-2007 at 08:05 PM.

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