A family wishes to purchase a heat pump for their home. The Get-It-Cheap Co. sells a heat pump that has an operating performance 38% of the coefficient of performance of an ideal Carnot heat pump. The price is $3200. For $5200 the Top-of-the-Line Co. sells a heat pump that has an operating performance 52% of that of an ideal Carnot heat pump. The family wishes to maintain their home at 21 ?C with an average winter outside temperature of -5 ?C. The family estimates that it will take an average of 21 GJ of energy per month to keep the house heated to this temperature for 5 cold months. The cost of electrical energy is $0.185/kWh (kilowatt-hour).
a. Compute the overall coefficient of performance for each heat pump.
b. Compute the cost of running each heat pump for 5 cold months.
c. How long will it take for the Top-of-the-Line heat pump to make up the cost differential?