Air-water heat pump with photovoltaics or pellet with solar

The larger the COP, the better.

How can you tell which ones are efficient? Sorry, I haven’t really dealt with the topic ...

Then I would strongly advise against a heat pump. It is a system that requires quite a bit of familiarization and attention. At least if you don’t want to be unpleasantly surprised by the electricity bill soon.

Why do you always rant so much against heat pumps? Are you selling gas heaters? :D Heat pumps aren’t that complex as long as they have been planned reasonably well.

I’m not campaigning against heat pumps. I have nothing against the technology, only against the lobby ;) What you describe is usually the problem though: poorly planned heat pumps by installers of the old school who can install gas and condensing boilers wonderfully but don’t understand heat pump systems. Our installer (with over 15 branches in Germany) wanted to sell us the same nonsense... heat pump, buffer tank, thermostats, bypass valve, etc. Everything that kills efficiency but guarantees him a quiet life.

Why? Obviously, so he can have peace during the warranty period, but efficient is something else. But it doesn’t matter, the customer pays for the electricity, not him. Heat pump systems simply don’t forgive planning mistakes like other heating systems do.

In the end, we decided against the heat pump, for exactly these reasons. He was not willing to be convinced to leave out the buffer tank and the bypass valve. I don’t see why I should finance that and then optimize endlessly afterward. If gas and heat pump had been the same price, I would have done it anyway. But with an additional investment of 3,000€ (including gas connection) which also needs to be financed, purely economic reasons spoke against it. I had considered horizontal ground collector, but it’s difficult on our property. That’s why, contrary to my opinion from a few weeks ago, it ended up being gas.

I am now planning for 10-15 years. Then the heating will probably be replaced and exchanged for a new heat pump of the latest generation. The money saved until then I will initially put into other things, such as repayment.

Your experience already confirms something - our HB is also rather inexperienced with WPs and originally wanted to install thermostats, buffer tanks, etc., but was quickly talked out of it – perhaps a bit too quickly (we now have 20 mm underfloor heating pipes – but okay). In terms of price – if I include the Bafa subsidy – it’s about the same as gas + ST ~ 15k € for heating (all inclusive) and drilling. Interestingly, what doesn’t work so well for us is the brine temperature – and the drilling company was very experienced... the winter will be "exciting".

At that price, I wouldn't have hesitated either, it's practically a giveaway. ☺ Just the drilling 2x75m would have cost us €11,000. I would never have made that back in this lifetime. Well... now let's see how the first winter will be. One advantage is: I don't stand worried in front of the electricity meter at subzero temperatures