Depending on the daytime, month etc. the demanded electrical power in the grid is varying a lot. https://www.energy-charts.de/price.htm
Due to that, the price per Kwh is varying as well. Now the question is:
Are there any demand driven electricity Feed-in tariffs in Germany?
In the last years, the amount of private electricity producers due to the EEG and the availability of technologies has risen a lot. There are many people having their own solar or wind power plant feeding eletricity into the grid. Battery storage tech is becoming cheaper, and easier available. It would make sense to produce electricity with renewable technologies and store part of that in battery storage. This capacity could then be fed into the grid only when the prices are high. Even after an intense search on the internet, I couldn't find any tariffs that would benefit such a demand driven approach.