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Homework Help: Watts to kWH per month

  1. Dec 6, 2009 #1


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    1. The problem statement, all variables and given/known data
    The question asks for us to go around our house, figure out the power usage of different devices, based on the estimated time use of these devices and calculate the total power usage per month.

    2. Relevant equations
    Energy = Power X Time
    Power = kW
    Time = hours

    3. The attempt at a solution

    Samsung TV
    Power usage @ 130.65W
    Usage @ 60 minutes per day (1 hour)

    (0.13065 kW)(1 hour) = 0.13065 kWh

    (0.13065 kWh)(31 days) = 4.05015 kWh per month

    Is that the correct way in trying to determine a given devices power consumption per month ?
  2. jcsd
  3. Dec 6, 2009 #2


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    Looks good.
  4. Dec 6, 2009 #3


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    Remember, when you multiply by 1 hour, what you're actually saying is it runs for 1 hour per day and thus takes 0.13065 kWh/day. If it ran for 8 hours, you'd instead have 8 hours * 0.13065kW per day giving around 1kWh/day.
  5. Dec 6, 2009 #4


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    yeah, that's what I've been doing for devices I have listed that run longer than an hour

    for example our washing machine

    1200W - 210 minutes @ 4 days per month

    1.2kW x 3.5h = 4.2 kWh

    4.2kWh x 31 days = 130.2 kWh/month
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