Air-to-air heat pump experiences?

But one should always think of the actual consumption costs, not just some paper values. And the LLWP performs well on paper, but otherwise (at least in my latitude in NRW) not. A neighbor has a Kfw55 (I "only" have Kfw70 according to the old Energy Saving Ordinance), but with his air-to-air heat pump he has much (!) higher costs (with less space) than I do with my ground-source heat pump. And I have the ground-source heat pump because there is no gas line, and it is one of the few options to keep up with gas in terms of consumption costs.

Apart from that, for a large part of the electricity used here, a flame is also ignited, which first heats water, it evaporates, drives a turbine (which is huge and heavy, and spins at 3000 rpm), and then the whole thing is transferred up and down again through several transformers, sent over tens of kilometers of cable, until it drives an electric motor that compresses gas and the resulting heat transfers the water in a heat exchanger of your heating system.

I find lighting a flame and heating water at home with high efficiency quite okay—by the way, as a rule: the greater the temperature difference, the more efficient, at least if you only want to transfer heat energy (or convert it into other forms of energy).

A neighbor has a KFW55 (I only have KFW70 according to the old Energy Saving Ordinance), but with his air-to-air heat pump, he has much (!) higher costs (with less area) than I do with my ground-source heat pump.

Are investment costs taken into account in this statement (with what depreciation period) or only monthly operating costs?

For now, only the monthly consumption. Since the investment costs are "hidden" for him (all-inclusive price for the house), it is not directly comparable. However, the ground source drilling typically lasts a lifetime, and furthermore, with the underfloor heating I am ultimately more flexible in choosing the heat generator (if there will be something better) in the future than with the air-to-air heat pump. If one assumes that his heating system cost the same as mine, excluding the drilling, then we are roughly even in total costs over the period in which I have paid off my loan.

Hmm, but if gas is available. What do I take then? For brine I have to drill, which costs a lot of money? Besides, geothermal energy has to be available first, it is not sensible everywhere? Basically, I have the options to take gas, or electric. I have admittedly not looked into brine yet.

The whole thing is available for €15,000 and turns the house into a KFW 40+ bunker, which in turn is subsidized with €15,000. For the air-to-air heat pump, that probably makes sense, but for gas?

As I understand what I've read here, you personally tend rather towards gas. You write above that the costs are virtually offset by the subsidy, and in addition, you get added value in the house through the thicker wall and the electricity storage + photovoltaic.

So for me, the situation is clear then.

You're right. But the Kfw 40+ applies if I take an air-to-air heat pump. If, on the other hand, I use gas, as I understand it, I can forget about KFW 40+ and fall back, for example, to KFW 55. But I'll follow up on that! I have an appointment with the friendly advisor on Friday.

I believe immediately that the thicker building envelope is an advantage and personally see no disadvantage in it. You? I lose about 2m^2 of living space because due to the thicker wall the house does not become bigger outwardly, but smaller inwardly. Unfortunately.

Regarding photovoltaic, the question arises for me about the current sense? The nice calculations of photovoltaic are based on the following facts:

1. It is assumed that the modules are new and remain new (which is nonsense)
2. It is assumed that the modules are spotless. Every pigeon dropping or layer of dirt would reduce the performance.
3. Generous sun hours are assumed
4. It is assumed that the storage battery maintains at least 80% of its nominal capacity for over 20 years. Practically a negligible memory effect. Can that be true?

That raises the question for me whether it makes sense, or whether one should give photovoltaic technology a few more years of development time. Especially the batteries. But here, too, I am really curious about your opinions, or better yet experiences.

Best regards,
laurooon