Air-water heat pump, gas, solar thermal prefab house, advantages and disadvantages?

Hello everyone,

I am honestly quite clueless by now.

This year we are building a prefab house, which consists of 2 bungalows each measuring 10.5 by 10.5 meters, separated by a flat roof corridor.
Fully basemented and under one bungalow there is a complete garage. (I don't know if that matters.)
We definitely have:
-floor heating
-controlled residential ventilation system with heat recovery
-and a fireplace – just for heating when we feel like it.

Currently, we are 2 adults and 2 children, it is not entirely impossible that another child will come into the world.

To be heated are the 2 residential bungalows, the corridor, and the 1 residential basement. So in total about 350 square meters.
Would you also somehow heat the garage with the central heating or connect it to the ventilation system? Because of the exhaust gases. The garage is used about 3 times a year for parties.

Geothermal heat pump is out of the question.
What remains is an air-water heat pump, heating oil, and gas.

Can you list the pros and cons of the mentioned heating options?
And would you basically plan with solar thermal or photovoltaic systems?
I at least know that nowadays you only cover your own consumption, but you are not sure if it pays off...

So I would be grateful for many tips and discussions, as we have to decide soon and I have no idea...

Thanks in advance.

Gas. Everything else requires deeper insight and is not as fault-tolerant. ST only if you have to. I would not recommend photovoltaics with gas - by the way, you can still sell electricity as long as the system is not over 10 kWp... it’s just usually not worth it.

We are not located on a gas line ... That means we would have to buy the tank .. Do you think it would still be worth it?

No. That is rubbish. Then air-water heat pump if brine-water heat pump fails. What design temperature do you have? (Does it get cold where you are?)

Yes, relatively cold. Osthessen, Rhön. I have often read that a heat pump especially consumes a lot of electricity at cold temperatures... And that after 1-2 people shower, only cold water comes out, etc., I definitely do not want something like that! Then I prefer gas, and you know that heat comes when you want it and the costs remain reasonable. How do you see that or what experiences do you have? I think the size of the house also plays a decisive role, right?

No. The size of the house itself doesn't matter... the heating load is decisive. The correct design of the heating system also plays a role. The amount of hot water as well. Hence the comment about the error tolerance. If all of this is calculated and taken into account, air-to-water heat pumps are wonderful alternatives - especially when no gas is available and everything else is ruled out. You can, of course, do whatever you want and believe whatever you want.