Physics

I only need help with part B.

A 250W computer power
supply is on 10 h per day.

Part A
If the cost of electricity is $0.15/kWh, what is the energy cost (to the nearest dollar) if this computer is used like this for a year (365 days)?
140 dollars

Part B
If this power supply is replaced by a more efficient 100-W version and it costs $100, how long will it take the decreased operating cost to pay for this power supply? (in years)

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  2. 👎 0
  3. 👁 100
asked by jen
  1. A. 0.250kW * 10h/day * 365days/yr. =
    912.5 kWh./yr

    Cost = 912.5kWh/yr * $0.15/kWh=$137/yr.

    B. (0.100/0.250) * 912.5kWh/yr=365kWh/yr

    Cost = 365kWh/yr * $0.15/kWh = $55/yr

    Savings = 137 - 55 = $82/yr

    $100/$82 = 1.22 Years.

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    posted by Henry

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