We are installing over 30 solar panels on our roof. The City of Austin currently offers a rebate up to $15,000 of 60 percent of the cost, and the federal government gives a 30 percent credit on the remainder. With those subsidies the rate of return on our own investment is 17 percent, making this is a superb deal for us.
A neighbor in the Netherlands has 4 solar panels on his roof, a strangely small number. I asked why. His answer: The Dutch government pays up to €1500 if you install a solar installation. Each solar panel costs him €450, with a fixed cost of about €200 for the installation. Thus his average rate of return on his 4 panels is about 25 percent, a great investment.