A typical electric water heater has an efficiency of 90 percent and costs $390 a year to o...

A typical electric water heater has an efficiency of 90 percent and costs $390 a year to operate at a unit cost of electricity of $0.08/kWh. A typical heat pump-powered water heaterhas a COP of 2.2 but costs about $800 more to install. Determine how many years it will take for the heat pump water heater to pay for its cost differential from the energy it saves.