ᐅ Which heating system is best for a household of 2 people, later expanding to 4?

Hello everyone,
I have read a lot of information by now, and I’m even more confused...
We are a couple, both 27 years old, and we want to build a house using prefabricated construction. We have researched companies carefully and narrowed down our options, and it will be a KfW 40 house.
Now the question about the heating system arises, and everyone tells me something different, whether they have already built, are currently building, or want to sell something (prefabricated house manufacturers).
Which heating system should we install for a household of 2 people, potentially up to 4 in the future?
The house will have about 160–170 sqm (1700–1830 sq ft) of living space and two full stories designed as a town villa. There will be no shading, and the house is planned to be almost square in shape.
Most suggest that we should aim for KfW 40+ and install an air-to-water heat pump with a photovoltaic system and battery storage.
However, someone else said that for a house like this, installing a photovoltaic system with storage is not financially worthwhile, as it would never pay off...
Could someone please help me?????

Unfortunately, there is no perfect all-in-one solution when it comes to heating systems; you will have to make some compromises.

For example, a gas boiler is very affordable, and in a well-insulated house with a central ventilation system, you may need very little energy. So, if your main focus is on a heating system that pays off quickly, this is a good choice. However, these rely on fossil fuels, which means they are not compatible with KfW 40 or 55 standards anymore.

If you prefer a good KfW rating rather than a quick payback, then design your photovoltaic system to make your home nearly self-sufficient. Use the energy you generate to heat the house and include storage as well. Since battery storage is currently (still?) quite expensive, you could also size your photovoltaic system large enough and initially do without storage, drawing electricity from the grid as needed. Later, when storage hopefully becomes more affordable, you can add batteries. I’m not sure how this approach affects the KfW rating.

The bottom line is: either you invest in a high-quality system that enables a nearly self-sufficient, environmentally responsible lifestyle, or you go for a system that pays off as quickly as possible. You will have to find a solution somewhere in between.

Many options are feasible, each with its own advantages.

I’m joining in here, as we will probably build something similar in size and the same design (just solid construction). I am also quite confused when it comes to heating and find it very difficult to determine what would be the right choice for us (also for 4 people later on).

I’m particularly interested in the maintenance aspect and space requirements. Which systems require regular filter changes or other maintenance, how long do the different systems last, and which ones take up the most space (especially relevant if building without a basement)?

For well-insulated houses with underfloor heating, a heat pump is usually a good option since high supply temperatures are not required. In this case, you essentially heat with electricity, which can be compensated for by installing a suitable photovoltaic system on the roof. Optionally, you can also add a solar thermal module to charge the buffer tank, further reducing electricity consumption.

Heat pumps are somewhat more expensive to purchase initially, but there are subsidies available, for example from BAFA. The more energy-efficient the house is, the more cost-effective a ground-source heat pump becomes, as the required area or drilling depth for the heat source naturally decreases. This results in lower collector costs while the subsidy remains the same (in our case, 4,500€ from BAFA for a ground-source heat pump with a smart grid certificate and buffer tank). This fully covers the cost of the collector.

I would say this... the more complex the system becomes, the longer the waiting times and the higher the maintenance costs. Because it simply takes more time. That’s why I am not a fan of suggestions like: adding another storage unit here... and another photovoltaic system there... plus some solar thermal on the roof so the house basically heats itself...

at all... and I would not recommend anyone install something like that in a single-family home. It will be a nightmare to control and the investments are substantial... and as mentioned, the maintenance will also increase. The system should be simple and efficient, not just a collection of every available option because there are subsidies or similar incentives.

We simply have a condensing boiler and domestic hot water support through photovoltaic panels. This way, I am in energy efficiency class A, and that’s good enough.