I won’t live long enough in my home to repay my investment in a solar system
Are you a blood relation of Ibn Batoota the eastern traveller, who was always travelling to various countries of the world? Or, a follower of Vasco De Gama the well-known western traveler? May be you are a dashing business executive who is always shifting to new jobs in new cities. Otherwise you should not be thinking like this. Thousands of house-owners of all ages are installing solar systems on their roof tops. People have calculated likely payback periods for solar systems. The financial payback period depends on a lot of factors. These factors include cost of electricity, magnitude of the load, daily usage pattern, incentives by the government, feed-in tariffs, the size of your system, and the local climate, among other minor factors. Various people have made calculations with various assumptions.
Two such reference calculations are available at the references[i] [ii] given below. Reference (2) did the calculations in year 2011, while calculations of reference (1) apply to year 2015. In either case, the payback periods calculated are between four and ten years. Reference (1) does mention that quite a lot depends on the local climate. In Germany and Japan, where sunshine is less, one can expect longer payback periods. Even within the United States South Western states like California expect much shorter payback periods because of the greater availability of sun. At the same time North eastern states have similar expectations of payback periods because of higher cost of electricity.
One should also note that money invested in a rooftop solar installation is not lost. It is an asset, and enhances the price of the house. If you do decide to sell it you recover more on account of the solar installation that you put in.
And, we need not always be money minded. We love, and actually need, a clean environment. We owe it to our generations that we leave this earth and its environment for them in a state cleaner than those are today.