The solar energy system has a very long payback time. The real savings/yield depend on the development of the electricity price and can thus fluctuate substantially, which one cannot be aware of during the time of investment. At the present level, the payback time is much over 20 years, in general. An annual return of 3 – 6 % can be expected for the investment. The return on the forthcoming years depends on the price development of the electricity.