Gas heating with solar thermal in new construction

I answered your question with a lot of text and very detailed, but then deleted my answer again because the decision for a gas heating system instead of a heat pump is not appreciated here in the forum.

Too bad, I would have liked to read it :)

A forum member has indeed replied. The same forum member has also already started a thread about how to best install it now so that you can switch quickly later. That should say it all. And hydrogen is nonsense. For heating systems in efficient houses as well as for most cars, etc. Only 20% of the energy actually reaches the end. With electricity, it's 80-90%. Besides, heating systems cannot simply be converted to hydrogen. Hydrogen will be reserved for applications that REALLY need this refueling option in the long term. Especially when you do the math. @TE If you really care about money: Skip solar, just use gas. Solar does not pay off. If you want a sensible solution with regard to costs: heat pump without photovoltaics. has an air-water heat pump in a new building, I believe 50-70€ heating costs per month. She can probably explain that better herself. Try that with a new gas contract. You can easily compare that.

with biogas

Where does that come from? And how much will it cost when fossil fuels are no longer allowed?
It's the same nonsense as "I only buy my pellets from sustainably managed German forests." You can do all that. But it is only enough for very few and will eventually become unaffordably expensive. And in the end, it doesn't change anything about CO2 emissions. It is in the air.

Operating heating systems with hydrogen is also possible, but it will always require about ten times more electricity than heat pumps. How this will ultimately affect the price, we will (probably not) see.

Biogas is only bio if corn is not specially purchased for it over dozens of kilometers or if grain is not used for it. We simply cannot avoid the fact that there will be no single true alternative. Everyone must reduce their energy consumption as much as possible and be economical. Daily 20-minute showers or grandma's warm room at 25 degrees are no more necessary than the trip on Sunday to the McDonald's 20 km away. ....I'm digressing...sorry

Yep. Currently, "energy crops" are grown on 2% of our national territory, just so there is a fig leaf at the gas station. The climate balance of these plantations is worse than using fossil fuels directly. Furthermore: if the same area were used for photovoltaics, we would already be on the sunny side of the energy transition and would have about a hundred times higher energy yield per square meter – I don't have the exact number in my head.

In short: biogas can only come from waste. However, that will likely only contribute in the per mille range to our heating demand.

Daily 20 minutes of showering or grandma's warm room at 25 degrees do not have to be any more than the trip on Sunday to the McDonald's 20 km away.

I am of the opinion that almost everyone sees potential for savings elsewhere. For example, I do not want to give up a warm apartment and daily showers, but giving up air travel, meat products, and increasing the world population is easy for me. I only have to drive a car in winter.