Combination of air-to-air heat pump, air-to-water heat pump, solar thermal and photovoltaic system with storage

Hello everyone,

I hope I am in the right subforum here.

About my project:
My wife and I will (expected start spring 2021) have a new building (KfW55) constructed. The usable area will be approximately 209m² plus basement.

With our developer, heating and hot water are realized via an air-to-water heat pump and an air-to-air heat pump including a fresh air system with heat exchanger. Additionally, we decided on a 6kWp photovoltaic system with a 6.5kWh storage (it was available as a "spring offer" for about €10,000).

Since I am personally more the type of person who tries to avoid unnecessary costs (in this case electricity costs for hot water), I considered having an additional solar thermal system installed. Without the photovoltaic system, I expect savings of about €200 per year (800kWh/year for hot water); if the household grows at some point, the savings will correspondingly increase.

In our last conversation with the architect, he was convinced that it would be more economical to expand the photovoltaic system to 8kWp (additional costs about €5,000) rather than to install the solar thermal system (he couldn’t give a price for this because it was not in the price catalog, but I assume a similar amount).

Now to my questions:
a) Does anyone have experience with similar energy combinations?
b) Are there contact points where you can have something like this calculated?

Thank you very much in advance and best regards
Kevin

Without a photovoltaic system, I expect savings of about €200 per year (800kWh/a for hot water); if the household grows at some point, it will be correspondingly more.

Photovoltaic systems are practically always worthwhile. Your price is also okay. I would have also estimated the solar thermal system at around €5,000. That means it produces cubic meters of hot water in summer that you don't need, and in winter it just sits there uselessly. If you really save €200 per year, the investment would have already paid off after 25 years. LOL Increasing from 6kWp to 8kWp should cost around €1,500. An additional cost of €5,000 is total rip-off. I and practically everyone here prefer photovoltaic. The excess energy in summer gets paid to you, unlike solar thermal. Therefore, a photovoltaic system pays off after about 10 years.

Forget the ST if you don't need it for any fulfillment of the subsidies etc. The water can be well heated with the air-water heat pump. In summer, the electricity for this comes from the roof. Also, don't forget a shading concept. Modern houses tend to turn into a sauna in summer. The air-air heat pump can then be installed for air cooling in summer (in addition to the main heat source).

Great, thank you all. I have now decided on the 8kWp system.

Heating and hot water realized by air-water heat pump and air-air heat pump including fresh air system with heat exchanger.

I flinched here. You are getting an air-water heat pump and an air-air heat pump? I hope you mean controlled residential ventilation and not air-air heat pump. Both together is complete nonsense, or rather the air-air heat pump is generally nonsense unless you are building a "real" passive house.

Hi,

yes, of course, a controlled residential ventilation system will be installed. However, this has an integrated air-to-air heat pump for heating or reheating the air (in addition to the heat exchanger). From its exhaust air, the domestic hot water is then generated by an air-to-water heat pump.

Regards Kevin