ᐅ Which heating system? Air source heat pump / gas / geothermal heating

Hello everyone,

we are building a single-family house with 155m2 (1,670 sq ft) and want to try to meet KfW55 standards (at least that is what is stated in the contract). Underfloor heating is mandatory. We are working with an architect who also acts as the general contractor, so the house will be delivered turnkey.

The challenges are as follows:
1. North-facing slope – no opportunity for solar panels
2. Sloped site – the ground floor (GF) will be partially built into the hillside at the back. The bedrooms will be on the GF, while the living area is on the upper floor (UF) with a level exit “onto” the slope. By embedding the GF on one side, we can have a reasonably flat garden at the top.
3. There are currently just two of us, but a child is planned in about five years
4. We want a large bathtub and will therefore need a lot of hot water
5. I like to ventilate frequently and thoroughly
6. The utility room is on the GF along with the bedrooms. Could there be noise issues?

Now about the heating decision.
Originally, especially my partner wanted a ground source heat pump. That is probably the best option in terms of quality and ecology, but it is very expensive.
An air source heat pump is of course an alternative, but I’m concerned about electricity costs in winter because I suspect that, especially the GF, will cool down quickly due to the hillside situation.
Our architect recommends a gas condensing boiler, saying this is standard for 80% of new builds. We actually wanted to move away from gas and oil, but electricity also involves fossil fuels – at least indirectly. Of course, this would probably rule out KfW55 compliance, but I think KfW70 would also be acceptable.

What are your thoughts?

I think heat pumps are not bad, but they are too expensive. From an environmental perspective, it only really makes sense if the electricity used to power the heat pump is generated sustainably. That means either producing it yourself using photovoltaic panels or similar, or ensuring that the electricity you “buy” for the heat pump is green energy. However, this is usually too costly for most people, so in my view, a heat pump is installed and people claim they have built ecologically, are independent from fossil fuels, and produce no CO2. That might be true for the user, but generally, the electricity is generated with significant amounts of CO2 or nuclear power... So, I consider heat pumps to be somewhat of a “greenwashing” solution. On top of that, they are still far too expensive. Essentially, they are just electric heating systems.
(This is just my opinion...)
I believe it only really “makes sense” if you produce the electricity yourself.
I consider gas heating to be the most economical option. Moreover, the focus should be on minimizing the energy required for heating in the first place—so good insulation and so on are much more important.
For us, a geothermal heat pump would have been about 15,000 euros (USD equivalent) more expensive than a gas heating system. With that difference, I can buy a significant amount of gas. Currently, we spend roughly 550 euros (USD equivalent) per year on gas (new build), so even if I estimate 700 euros (USD equivalent) annually, I could buy gas for over 20 years before breaking even on the extra cost. (This calculation doesn’t even consider that I would still have to pay for the electricity to run the heat pump. So, there might be an additional minimum of 30 euros (USD equivalent) per month in electricity costs for the heat pump?) The question then is whether the heating system will last that long. I can hardly imagine a heat pump running efficiently and sensibly for 30 years. Also, I’m not willing to invest in something that only pays off after more than 20 years and provides a kind of return on investment.
Imagine going to your bank to invest 15,000 euros (USD equivalent) and being told, “Great, but you won’t see any interest or returns for at least 20 years...” (which is kind of the case now).
I would rather invest in a new, more efficient heating system in 10–15 years than be stuck with a heat pump for so long just to make it pay off.
One alternative could be a pellet heating system. However, that requires storage space.

Best regards

mcarstensen, my heat pump with a collector costs a maximum of 12,000 euros, who compared apples and oranges in your case?

And after how many years does a house, car, or mobile phone pay off?

Points 4 and 5 from the technical expert are not particularly favorable for heat pumps; whether this is decisive enough to choose a different heat source can probably only be accurately answered by a professional.

Thank you for your responses.
I had also considered a pellet heating system, but we have issues with storage space. No basement, no attic; for a lot of money, we are digging a large garage into the slope, which will have to serve as a basement at the latest when we are three or four people. Therefore, it is probably not an option.

With a KFW55 house, hardly any heating is needed – the bigger issue is the large water tank, since it also needs to be kept warm.
Whether your house is built into the ground or is freestanding doesn’t really matter – the building envelope is so well insulated that hardly any heat is lost. However, if you lack sufficient window area, it will be interesting to see how you intend to achieve KFW55 standards!
I can only recommend involving a professional heating planner, including a heating load calculation. Without this, it will always be a matter of guesswork.

@mccarstensen:
Is the 550 euros only for heating? What about the cost for domestic hot water?

I'm also curious how we are supposed to achieve KfW 55 standard. We obviously can’t have many windows on the ground floor, but upstairs there is a large window façade facing both north and south.
I thought you shouldn’t install too many windows, though?

Is an air source heat pump feasible in the sleeping area?
My gut feeling is that we are between geothermal and a gas condensing boiler; however, the air source heat pump might be the most practical compromise?