Heat pump experiences - assessment?

Could it be that your misunderstanding lies in the function of a heat pump? A heat pump does not use the electrical energy applied directly for heating but to extract heat energy from the environment, transport it into the house, and raise it to a level suitable for heating. It does this so efficiently that the heating energy is about 3-5 times higher than the electrical energy used.

The energy content of gas is directly converted into heat through combustion.

At least, that is my understanding.

Yes, you are right, that's true. So what does that mean overall? As far as I know, gas currently costs less than one-third of electricity despite everything. Do heat pumps actually produce more than three times as much heat as gas heating systems at any operating point (and if so, which one?) in relation to their energy input?

If the entire heat pump heating system is well designed, the factor on average (annual performance factor) is significantly above 3. Whether a heat pump is worthwhile in your specific case may possibly be told to you by a heating engineer or energy consultant.

Okay, I think I am getting closer to understanding the matter after I just googled this [Jahresarbeitszahl]. Above a [Jahresarbeitszahl] of 3, the principle essentially compensates for the higher electricity costs (as long as these are three times as high).

What does this number mainly depend on? Is it possible, assuming a typical modern air-to-air heat pump and that you continuously have a modern underfloor heating system, to roughly estimate this "energy demand" of the building, which is basically given on every energy certificate in kWh/(m2*a)?

Something like "100 corresponds to a [Jahresarbeitszahl] of 3, 50 to 4, 150 to 2"?

Thanks in advance for the input so far!

That stands and falls with the choice of the heat pump, the plumbing, and the heating surfaces.

If the three factors are well chosen, you can achieve something between 4 and 5 in any reasonably insulated house (roof and windows). Three is actually already worst-case with a new heat pump. Something went wrong there. Often oversized, with setback temperatures activated, built-in buffer tanks, individual room control active... typical plumbing porn.

With gas, always add the gas connection, basic fee, chimney sweep, and maintenance. The efficiency of a gas boiler is also rarely at 90%. So you have to calculate that as well. All of this is eliminated with a heat pump. I believe there are only a few old contracts left that financially compare to a proper heat pump installation. New gas contracts are hardly available anyway, so you can save yourself the calculation.

That burning gas under any circumstances should be avoided is only mentioned in passing because no one has done it yet.

Ps: The numbers you mentioned above are easily achievable with radiators. With surface heating, you can add plus 1.

It all depends on the choice of the heat pump, the sanitary system, and the heating surfaces.

If these three factors are well chosen, you can achieve something between 4 and 5 in any reasonably insulated house (roof and windows). Three is actually the worst case with new heat pumps. Something must have gone wrong then. Often oversized, night setbacks implemented, buffer tanks installed, individual room control active... Just sanitary porn.

Cool, many thanks already for the tips! A few detailed questions regarding this:

[*]Do you mean by choice of the heat pump simply the right size? Or is it a simple quality question (invest more money = better coefficient of performance)?
[*]What is wrong with night setback and individual room control? Our previous heating behavior was mostly "leave the room = heating off". I understand that this wouldn’t work anymore with underfloor heating anyway, but it would be stupid if we have to run the heating full blast all year just to achieve a good efficiency, while actually consuming considerably more energy than before in absolute terms.

Ps: The numbers you mentioned above are easily achievable with radiators. With surface heating, you can add 1.
Ps: The numbers you mentioned above are easily achievable with radiators. With surface heating, you can add 1.

So you mean a heat demand of 100 means a coefficient of performance of 3, with underfloor heating even 4? How well can energy consultants usually predict this number? Are there often nasty surprises?

Thanks and regards

Mainly, when I say "proper heat pump," I actually mean the size. Also great is an environmentally friendly refrigerant, and by an extremely wide margin, only R290 should be mentioned here. It is the most efficient, cheapest, and at the same time the most environmentally friendly refrigerant on the market.

It feels strange at first, but: As soon as a house has windows (so not >200 kWh/sqm), partial heating, night setback, on-off heating is not only terribly uncomfortable but also actually consumes MORE energy. You don't have to believe me; you can gladly read up on it yourself in various studies.
This is mainly (and especially with heat pumps) because such heating behavior requires a higher flow temperature to be produced. The higher this is, the more inefficient the heating systems run, especially heat pumps.

If you have a thermal envelope (house), you should keep the entire envelope as evenly as possible at your comfort temperature 24/7. Or happy to keep it permanently lower if you want to save, but not sometimes like this, sometimes like that.
You have already recognized one reason for this: With surface heating and a properly sized heat pump, you CANNOT just quickly heat a room up by 5°. It takes a whole day. Second point: If you have many cold rooms and only heat the living area, you not only have to put in the energy actually needed for the room but also compensate for the adjacent cold walls. So you have to provide EVEN higher flow temperatures to have it reasonably comfortable in that one room. And this actually unnecessary overheating of the heating water generates more losses than you could ever save.

So: as soon as you have a condensing boiler or a heat pump: set the desired room temperature directly at the valve (radiator or underfloor heating) via hydraulic balancing, lower the flow temperature as much as possible, and let it run!

Your last point, with the numbers: these are already very, very rough estimates. Actually, it doesn’t work so generally; I just wanted to put it into some context.
Energy consultants usually can't do much except grab subsidies. If you really want reliable figures, you need a proper engineering office. They calculate your heating load and your underfloor heating design.
With that (and only with that), you or a sanitary engineer experienced with heat pumps can select the right heat pump and maybe make an estimate of the seasonal performance factor.
But even if all that is done correctly, and then you start to cripple the heat pump with single-room control and night setback, the seasonal performance factor will quickly be a number smaller again.
So many factors influence it. And by far the most important one is the one you are already beginning to influence now: your knowledge about your future heating system.