But no heat pump in a single-family house?

the construction costs of solar utilization are in the six-figure range.

.. that's exactly the point ... and if you then have to repay this six-figure financing amount as a loan and amortization, plus maintenance and operating costs, you can calculate for yourself where and how such a cost-benefit calculation will look in the end ...

Good day, 1.5 years ago I conducted an energy consultation for a small house from the 1950s, actually the house is a disaster. Blowing out the air layer always ended in the calculations with "waterlogged walls," so another approach had to be taken.
So I planned the following measures there.
-Bricking up radiator niches
-Insulating roller shutter boxes
-Replaced windows, now U-value 1.2 (so that they are less well insulated than the walls)
-Insulated roof and top floor ceiling
-Insulated basement ceiling
-Replaced radiators and pipes
-Solar support for heating and domestic hot water on the roof
-Equipped existing chimney with a water-guided insert (theoretical efficiency 84%)
-A tiny gas heater
-A large storage tank
The KFW approved the project through 152 and the customer received his favorable loan.
The customer is highly satisfied, the gas heater barely runs, only on days when there is no sun and nobody has time to stoke the chimney.

Regards, Jürgen

With this I want to say, your architect’s idea works well. On the other hand, such a heat pump naturally requires quite a bit of electricity.

....-existing chimney fitted with a water-guided insert (theoretical efficiency 84 %)

An efficiency is always power-related and merely a lab snapshot, nothing more. It is often misused for advertising purposes. The decisive factor is the heat generator expenditure ratio, since the operator has to pay for energy and not power!

...The KfW approved the project through the 152...

That only means that their requirements/conditions were met on paper. Actual profitability for the operator cannot be derived from this. Other interests are in the foreground here ;-) Furthermore, a low interest rate is hardly synonymous with profitability; even a compulsory initial grace period increases the total cost of financing, especially with investments sometimes considerably exaggerated by the requirements.
If you take the easy way out, you blindly believe in benefactors ;-)

...On the other hand, such a heat pump obviously needs quite a lot of electricity.

If you reduce the demand beforehand, every heat generator consumes less! ;-)

Best regards.

An efficiency is always power-related and merely a laboratory snapshot, nothing more. It is often misused for advertising purposes. What matters is the heat generator effort factor, since the operator has to pay for energy, not power!
That only means that their requirements/conditions were met on paper. However, an actual economic viability for the operator cannot be derived from this. Other interests come first here ;-) Besides, a low interest rate is hardly synonymous with economic viability; just an initially compulsory grace period on repayment increases the total cost of financing, especially with investments sometimes far exaggerated by the requirements.
If you keep it simple, you blindly believe in benefactors ;-).
If you reduce the demand beforehand, every heat generator consumes less! ;-)

Best regards.

Regarding the efficiency, it also explicitly and clearly says "theoretical efficiency."

I am not a benefactor but have done what one can do with such a place; if the customer has now bought such a house and has a certain budget for the renovation, including the desired KfW loan, then I strive to make the best out of it. Here one distinguishes between practitioners and theoreticians.
If he had asked me before the purchase, I would have rather advised the customer against buying.

The demand was lowered as much as possible, but some things simply could not be done. Therefore, the focus was on solar and wood here.
Specifically, the customer also has the opportunity to get wood cheaply.

The customer is satisfied; the gas heating hardly ever runs. From that perspective, I think I didn't do too badly.

On the subject; if you now have a house insulated to today's standard, the system works. That was what was asked.

An air heat pump is calculated by the average building technology specialist company with 1 kW of electricity input for 2 kW of heat output – at least the ones I know. Okay, you can find that much or little; personally, I don't find an air heat pump that great.

And finally, I certainly haven't swallowed wisdom with a spoon and like to learn every day.

Best regards from the beautiful Tecklenburger Land

Jürgen Wegener

...I am not a benefactor ...

The addressees were others!

.. Here one distinguishes between practitioners and theorists. ...

As an expert, I am by no means a theorist, if that was what was meant. On the contrary, the insights gained from practical systems are taken into account in my planning!

.. ..The customer is satisfied, the gas heating rarely runs. From this I think that I have not done too much wrong.

If a customer is satisfied and there are no possibilities for comparison, one should not interfere! ;-) If a gas heating system rarely runs, the question of its justification should be asked ;-) No one acquires something in order not to use it or only use it little! One first optimizes what is available before undertaking additional, sometimes uneconomical effort. This distinction usually fails for laypersons; sellers naturally advise additional investment ;-) A knave who thinks ill of this ;-)

.. if one now also has a house that is insulated according to today’s standards, the system works.

Purely "working" or merely "making warm" could be attributed to almost anything. Today, due to the now high investment costs, this is clearly not enough. High investment must bring sustainable savings in operating costs, not on paper but in reality. Here is usually where the paths of sellers and competent specialists diverge.

...An air heat pump is calculated by the average building technology specialist company with 1 KW electricity in, 2 KW heat output out - at least those that I know.

Whether these are "specialist companies" I would strongly doubt. Presumably they only sell oil, gas, pellets... Well-planned air heat pump systems achieve a yearly performance factor of about 3.5, although this does not reach that of brine systems with a yearly performance factor of about 4.5..4.7, but for these no additional costs are needed for source development.

... Ok, one can find that much or little, personally I don’t find an air heat pump so great.

Personal feelings are subjective, by no means objective. Therefore hardly a suitable, independent advisor. Only facts count here – not one’s own, certainly well-meaning, sentiments.

..I certainly have not swallowed wisdom with a spoon and like to learn something new every day.

The same applies to me; every measurement and investigation in practical systems contributes to gaining insights for future projects!

v.g.

The recipient was someone else! As an expert, I am by no means a theorist, if that was meant. On the contrary, the insights gained from practical systems are taken into account in my planning! If a customer is satisfied, and there are no comparison options, one should not touch that! ;-) If a gas heating system hardly ever runs, the question of its justification for existence should be asked ;-) No one acquires something to not use it or use it very little! First, one optimizes what is available before undertaking additional, partly uneconomical efforts. This distinction is usually not made by laypeople; salespeople naturally advise additional investment ;-) A knave is who thinks evil in this ;-) Purely "functioning" or merely "warming up" could be attributed to almost anything. This is clearly too little today, due to the now high investment costs. High investment must bring sustainable consumption cost savings—not on paper, but in reality. This is where the paths of salespeople and those of the competent professionals often diverge. Whether these are "specialist companies," I would strongly doubt. Presumably, they only sell oil, gas, pellet... Well-planned air heat pump systems achieve an annual performance factor of about 3.5, which does not quite reach brine systems with an annual performance factor of around 4.5..4.7; however, no additional costs for source development are required here.

Personal feelings are subjective, by no means objective. Therefore hardly a suitable, independent advisor. Only facts count here—not one's own, certainly well-intentioned, feelings. The same applies to me; every measurement and investigation in practical systems helps to gain insights for future projects!

v.g.

€uro, you are quite something! What you say is off-topic, but never mind, I am evil and stupid and you are the hero. A factual discussion with you seems pointless to me. I will no longer participate in the discussion because I have more important things to do.

Have fun, Mr. Expert €uro.

Regards, Jürgen Wegener