Pool construction simultaneously with house construction - Your assessment

With a heat pump, the KFW should actually not play a role. The heating capacity is without the pool. I am rather skeptical whether you can get a device with indoor installation in this performance class. Therefore, I would rather take a separate heat pump. Then you will have no problems with KFW or anything else.

We are talking about 31.2 m3 of water. The heat pump should have at least 20 KW. Otherwise, you won't get the water warm for weeks and you also can't keep it at higher temperatures when it gets colder.

Take the automatic backwash. Even if the filter is not dirty, it should be backwashed weekly. Otherwise, channels will form and the filter performance will decrease. The material usually has to be replaced earlier then anyway.

We were advised by all the pool builders we spoke to to use a separate heat pump for the pool. And the first thing the plumbers all said was that the pool must have a separate heat pump; anything else makes no sense in terms of performance. Since I am not responsible for technical matters here, I unfortunately cannot provide more details on how exactly the calculation was done.

For us, pool technology is deliberately not installed inside the house. Acquaintances had a minor water damage due to a defective lifting system, but the drying, including drilling up the screed, was extremely elaborate despite the few liters of water, so we were uncomfortable with the idea of directing pool water basically into the house. Except for one pool builder, all the others also advocated on their own for not placing the technology inside the house for these reasons.

In any case, I would also opt for an automatic backwash; nothing else was an option for us after sometimes forgetting to check it with the current pool...

Performance-wise it doesn't matter. We have a 110m3 pool and operate it with the primary heating system. The technology in the house is great. You just have to secure it through processes, sensors, etc.

If I remember correctly, we would have had to use a significantly larger heat pump for the house, and there was something else related to the cooling function, but I can’t quite recall. Our acquaintances had a sensor on their lifting system that also gave an alarm, but unfortunately no one was home and eventually it overflowed. That is certainly technically much better and safer, especially for the pool, but the effort wasn’t worth it to us. And if you or rather a woman has a bad feeling, you just can’t argue against it. We are now combining the equipment room with the garden shed that is already there anyway; I also wouldn’t have wanted a shaft for the equipment.

He recommended the larger heater instead of an additional heat pump, but also immediately expressed concern that this might cause problems with the KfW subsidy due to poor energy consulting. Do you have a gut feeling about this?

Calculate how much the KfW subsidy really benefits you in the end, and how much extra effort and money you need to invest to achieve this goal. Many people disregard this subsidy and forego it for a reason. (It's the same for me.)