Q:How long will it take for solar to "pay itself back"?
A solar energy system is an investment like many others, and should yield a good return immediately. Consider how much money the solar energy system saves you on an average monthly or annual basis.Then compare this with the "opportunity cost" of the money that the solar system costs. The "opportunity cost" is either what the money costs to borrow, or the money that you forfeited by taking the money out of another investment.
If you are not making money immediately, perhaps the solar system is not a good investment and you should not build it. A solar heating system that does not make good economic sense often does not make environmental sense either.
Cost benefit analysis for a solar energy system in the Boston, MA area predicts that the investment will yield about 12% per year. If the cost of conventional energy such as fossil fuels goes up in the future, the value of the solar investment goes up, too. You should keep in mind that the income from the solar investment is tax-free. More information about cost benefit is available in the US Department of Energy Report. (in the INFO LIBRARY) http://www.radiantsolar.com/pdf/DOEREPORT.pdf
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