1) Would a solar water-heating system be more cost-effective for a homeowner with electric resistance heat, or a homeowner with natural gas heat?
Answer: A solar water-heating system would be more cost-effective for a homeowner with electric resistance heat because electric energy is more expensive than natural gas for water heating.
2) What is the payback period range for the 2-kW PV system example (given above) that is connected to a utility that charges $0.08 per kWh? For $0.25/kWh?
Answer: For $0.08/kWh, the simple payback ranges from 87 to 109 years. For $0.25/kWh, the simple payback ranges from 29 to 35 years.
3) What are the payback period changes for the conditions given in question 2 when the federal tax credits are factored into the calculations?
Answer: The installed cost factor can be reduced by $2,000 – for $0.08/kWh the simple payback ranges from 76 to 98 years; for $0.25/kWh the simple paybacks range between 24 and 31 years.
4) How does switching from electricity to natural gas or fuel oil change the simple payback for a solar water-heating system?
Answer: Switching from an expensive fuel to a cheaper one increases the time it takes to pay back the cost of the installed system.