ᐅ Air-to-water heat pump, gas heating, solar thermal systems in prefab homes – advantages and disadvantages?

Hello everyone,

I am honestly quite at a loss.

This year, we are building a prefab house consisting of two bungalows, each measuring 10.5 by 10.5 meters (34 by 34 feet), connected by a flat-roofed corridor. The house is fully basemented, and under one bungalow, there is a garage. (I’m not sure if that matters.)

We definitely have:
- Underfloor heating
- A mechanical ventilation system with heat recovery
- And a fireplace, just for supplemental heating when we feel like it.

Currently, there are two adults and two children living here, and it’s not impossible that a third child might be born.

The areas to be heated include the two living bungalows, the corridor, and one finished basement area — in total about 350 square meters (3,770 square feet). Would you also heat the garage with the central heating or connect it to the ventilation system? Considering the exhaust fumes. The garage will otherwise be used for gatherings about three times a year.

A ground-source heat pump is off the table. The remaining options are an air-to-water heat pump, heating oil, and gas.

Could you list the pros and cons of these heating methods? And would you generally consider planning with solar thermal systems or photovoltaic panels? I know that nowadays they mainly cover your own energy needs, but it’s still uncertain whether they pay off...

I would really appreciate lots of tips and discussions, as we need to make a decision soon and I have no clue.

Thanks in advance.

Gas. Everything else requires deeper knowledge and is less fault-tolerant.
Gas heating only if you really have to. I wouldn’t recommend photovoltaic systems with gas – by the way, you can still sell electricity as long as the system does not exceed 10 kWp (kilowatt peak)... but it’s usually not worth it.

We are not connected to a gas line... so we would have to purchase the tank ourselves. Do you think it would still be worth it?

No. That’s nonsense.
Then an air-to-water heat pump if a ground-source heat pump fails. What design temperature do you use? (Does it get cold where you are?)

Yes, it is relatively cold.
East Hesse, Rhön.
I have often read that a heat pump can consume a lot of electricity, especially at low temperatures... and that after 1-2 people have showered, only cold water is left, etc. I definitely want to avoid that!
I would rather choose gas because you know that heat will be available when you want it, and the costs remain manageable.
What are your thoughts or experiences?
I think the size of the house also plays an important role, right?

No. The size of the house itself doesn’t matter... the heating load is what counts. Proper sizing of the heating system also plays a role, as does the amount of hot water needed. That’s why I mentioned the margin for error. When all these factors are calculated and considered, air-to-water heat pumps are excellent alternatives—especially when gas is not available and all other options are ruled out.
Of course, you can do and believe whatever you want.