Heating concept for discussion: gas, solar, and wood

Happy Easter everyone.

We are building a city villa with 2 full floors and approx. 200 sqm of living space. There will be a total of three bathrooms (main bathroom with bathtub, children's shower bathroom, guest WC). We are building to the KFW-55 standard. From mid-year, there will be three of us. A fourth pair of feet is already in planning in our minds.

The developer offers an air-to-water heat pump from Novelan LAD 7 CSD. A controlled residential ventilation system is already planned.

However, I would like to discuss a different concept with you: gas condensing boiler plus solar thermal, large buffer tank, and fireplace/pellet stove with water jacket.

My idea behind this: I think solar thermal is reasonable. Even with an air-to-water heat pump, I would include solar thermal. The large buffer tank would therefore already be a topic for us. We want a fireplace/pellet stove in the living room anyway. The extra cost for the water-connected version would therefore be absolutely acceptable.

I do not want to talk about the basics of the advantages and disadvantages of the air-to-water heat pump compared to a gas condensing boiler, but rather open my concept for discussion. Do you have any ideas or suggestions for me?

Gas condensing boiler is solid technology. If it breaks down, the replacement is by far not as expensive as with the air-water heat pump. The controlled residential ventilation with heat recovery and the chimney on top is OK.

Gas condensing boiler is solid technology. When it breaks down, the replacement is by far not as expensive as with the air-to-water heat pump

...and I thought it wasn't supposed to be about fundamental discussions [emoji849]

I am not an expert in heating technology, but a few general thoughts that are repeatedly mentioned in similar discussions.

- A water jacket "is never worth it." At least economically speaking. Whether that matters to you, I do not know. Is the "acceptable surcharge" based on a concrete offer or your assumption that "everything necessary is already there"?

- Solar thermal and heat pumps require at least significant planning effort because one is low temperature, the other high temperature.

- When it comes to the size of the hot water storage tank, it is less about the space requirement and more about the energy needed for germ-free operation, i.e., regular reheating.

PS: Our heating choice is not yet final; the preference would be a brine heat pump. But if gas, then I will try to avoid solar thermal. With our current [ST], there has been trouble for years.

- A water bag "never pays off." So economically speaking. Whether that is your concern, I do not know. The "acceptable surcharge" is based on a concrete offer or your assumption that "all necessary things are already available anyway"?

It is actually based on the assumption that all necessary things are already there anyway.

- Solar thermal energy and heat pumps require at least considerable planning effort, because one is low temperature, the other high temperature.

Good argument. Thanks.

- Regarding the size of the hot water storage tank, it is less about the space requirement and more about the energy effort for sterile operation, i.e. regular reheating.

That is correct. However, regular reheating is not too difficult to manage with my concept, as solar thermal and the water bag regularly provide sufficiently hot water.

The ST only supplies hot water roughly between May and September. The water pocket is an absolute mess at 55... in order for it to be of any use at all, the stove has to deliver proper heat. But that contradicts the rest of the house concept.