Great idea, but it has too many mistakes:
1. Most people in Germany do not have their own house, but live in rented apartments. They have no possibility to install any kind of power generator, renewable or not.
2. Even if you have your own house, you cannot install for example a wind turbine or a biogas tank - these are only allowed at a minimum distance to living areas.
3. So, the only option is the solar power, but its output is fluctuating, so you need capabilities to equalize it, either:
- keep a connection to the grid (which brings you back all kinds of taxes and fees back, also see the next point)
- have a battery storage - for a househould it would require a battery the size of a shipping container and cost 1-2 million euros and wear out within few years. Remember, you need a storage capacity to last through the winter, where there is barely any solar output.
- have a backup generator running on diesel or gas - possible to combine with a heating boiler, there are solutions on the market like that, but then again you will need to pay additional taxes for electricity generation from gas, pay for gas, deal with the waste heat when you don't need it and I don't think any solution will readily run without grid connection
4. Starting from this year, the regenerative energy produced for self-consumption will be also subject to the EEG surcharge (the money that goes to the subventioning the renewable energy production) in Germany.
When you realize that it's cheaper for you to live off the grid you will realize that it's cheaper not to live here at all.