That does not cause any problem. This is done everywhere, including Germany. It is very easy, technically speaking, to incorporate this electricity into the grid. When solar energy is being produced, dams, nuclear power plants and coal-fired plants produce less energy. There's simply no technical problem involved in doing this. It can be done now.
There will be no problem if we introduce legislation whereby consumers who decide to use solar energy will get a return on their investment in the form of solar kilowatt/hours. There will be a leverage effect in the market. This will be done automatically, as happened in a number of European countries in particular.