"Furthermore, that $3,000 is a guaranteed return unless you assume that electricity prices will go down over the coming years. Don't hold your breath. If anything, prices will rise. Today's $3,000, then, could be more like $4,000 or $5,000 of free cash flow to spend on other things instead of electric bills 10 years from now."

An example was used of a 30K expenditure. You could spend this on a car, put it in the bank at a whopping 0.5% interest or you could put it on your home's roof and more than likely decrease your electric bill to a few dollars a month or eliminate the electric bill altogether, for life. It all comes down to what do YOU justify spending your money on and how do YOU JUSTIFY the purchase that you make. Piss it away on a car and have a continous money sink that requires fuel, insurance, maintenance until you go out and get into debt to buy another one. Put the money in the bank at a whopping 0.5 to what 1.5% which wouldn't pay for one electric bill a month all year long. Put it on your home and get rid of the monthly electric bill for decades to come.