
131Economics of Energy Generation and Conservation Systems
2.7 A rooftop solar hot water heater with collector areas of 8 m
2
and storage of 640 L is
installed in Phoenix, Arizona, on a house that uses 160 L/day of hot water at 60°C.
Of the total energy required, 70% is supplied by solar energy (the solar fraction is
70%) and 30% is supplemented with an electric heater. The solar system costs $3000
for installation, whereas an electric water heater and tank for the same supply costs
$800 for installation. Assuming that the electricity cost is $0.10/kWh and does not
change over time, estimate the simple payback time for the solar hot water hea ...