New build bungalow - air-water heat pump, photovoltaic and solar thermal?

Drilling here at a company costs about €12,000.

The depth of the drilling depends on the heating load of the building and the geothermal yield of the ground. So first calculate the heating load, then have the drilling depth calculated (and don't just let a drilling company start guessing). For €12,000, I could have a drill hole about 200m deep based on the given price indication. This corresponds to an extraction capacity suitable for a small multi-family house. I also hardly believe that the Lower Saxony region is supposed to be that much more expensive – there is probably a rip-off at work in your offer.

Since the sun is not that intense in our regions, I hope to increase self-consumption with the photovoltaic system using a storage unit.

If the photovoltaic system alone is already unprofitable, then the storage will not improve this situation. On the contrary, then both are nonsense. Have you ever calculated with pvgis?

I wouldn't say unprofitable, it just takes a few years. Or am I wrong about that?

As for the costs with storage, I would have to calculate with a solar installer.

I haven't calculated in [pvgis] yet because I didn't know it before. But I will do it. Let's see what comes out of it.

I wouldn’t say unprofitable, it just takes a few years. Or am I wrong about that?

Well, if the ROI occurs after 20 years (my calculations with storage go well beyond 40 years ...), there is a certain probability that the components will be defective by then. Storage manufacturers usually offer a 10-year warranty on 80% of the capacity, after that ... good luck.

That's true, it is the local company that has never been cheap. The city is providing a €2000 subsidy, and since then the price has risen from €10,000 to €12,000. However, I haven't heard of anyone in my circle paying less than €8,000. With a low heating load and a low standard outside temperature, I would really prefer the air-to-water heat pump. And definitely one that can modulate properly.. But the ground-source heat pump is actually more efficient. And above all, of course, possibly interesting because of the subsidy, which can hardly be achieved with the air-to-water heat pump

After many numbers, it is clear to us for now that there will be no photovoltaic storage system. A photovoltaic system in the area of 6kWp should be profitable for us after about 10 to 11 years, depending on costs. That is okay for us.

Regarding geothermal energy, I have already read quite a bit. What about maintenance of the collectors or maintenance of the entire system?