Question

Suppose that there are two alt electric motors that provide 100hp output. An Alpha motor can be purchased for $12,500 and has an efficiency of 74%, and estimated life of 10 yrs, and estimated maintenance cost of $500/yr. A Beta motor will cost $16,000 and has an efficiency of 92%, a life of 10 yrs, and annual maintenance costs of $250. Annual taxes and insurance costs on either motor will be 1.5% of the investment. Assume that SV for both motors are negligible and that electricity costs $0.05/kw hr.

Note: Electrical Eff = output power/input power, and 1 hp = 0.746 kW

If the MARR is 15%, how many hrs/yr would the motors have to be operated at full load for the annual costs to be equal?

Answer 1