A kilowatt hour (kWh) of electricity currently costs around 42 cents in Germany (including electricity price cap). With a photovoltaic system you can generate your own electricity. This means you save on every kilowatt hour you use.
If you install a photovoltaic system, your annual electricity costs will drop significantly. If you combine the system with an electricity storage system, you will increase your savings even further. With an electricity storage system, you can use your own solar power even when the sun is not shining, thus reducing the amount of electricity you draw from the grid.