Operate heat pump autonomously with photovoltaic system.

If you would explain your calculation to me, I would gladly show you mine. Then we can compare

Why do we need a calculation for that? It should be obvious that a several hundred square meter property with a >100 sqm house with its construction costs is not "economically" habitable by a family of four.

This is pure luxury! It has absolutely NOTHING to do with economic efficiency, which for you is apparently at the top of the list...

However, I would still be interested to see how you nicely calculate your KfW40+ house.

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You are right. But don't be too hard on the OP.

The decision to buy a single-family house is usually not based on a business case that is green. Even experts say that.

The decision is usually made based on other criteria.

In a way, it is a luxury – or the desire to shape one’s private life situation according to one’s own ideas (if you can do that, it is, in turn, a kind of luxury, yes).

What the OP surely means is: Given the decision, be as economical as possible…..(again from the perspective of his own criteria catalog. Anyone can make the numbers look good – see my post above, but it is legitimate to do so, no shame! One person is happy about low investments, another about savings afterward from an investment made).

Best regards, Thorsten

The decision is usually made based on other criteria.

This statement is unmistakable:

Thank you for your tip. The possible expansion of the system is of course logical and the result understandable. But for me, profitability is the top priority.

@oleda. The OP means that he personally considers it economically viable (from his perspective) to make investments. From a purely business management perspective, you are still right! I am not contradicting you here.

There is nothing to add to the last posts you wrote in this thread. Very good posts.


Sometimes you make it difficult.
The OP primarily meant regarding economic efficiency that (referring to my example) it is completely uneconomical to install an absolutely oversized photovoltaic system on the roof just to cover the self-consumption as much as possible. <-- with which I absolutely agree.

You mean that often the investment in land and house - purely from a business perspective - is not economical. Although this is not always necessarily the case. A few months ago I described in a thread using the example of a colleague that there are areas where the investment already pays off based on the land price (my colleague paid about 120 euros/sqm three years ago - today people in his community put about 300 euros/sqm on the table for a similar location).
Where you are also right - the investment in a KfW55 house/KfW40 house often does not pay off in the medium term either. There was also a thread about this recently again.

But - as far as the OP has thought in this direction at all so far: This was not the starting point of his question. His interest/his question is to what extent a as high as possible degree of self-sufficiency can be achieved, or whether this is generally uneconomical and what the experiences are in this regard.

Why do we need a calculation for that? It should be obvious that a several hundred square meter property with a >100 sqm house with its construction costs is not "economically" habitable by a family of four.

It is pure luxury! That has absolutely NOTHING to do with economic efficiency, which for you ranks at the highest priority...

But I would still be interested in how you nicely calculate your KfW40+ house.

I don't understand how one can insist on the opinion that a house is not economical. Maybe we misunderstand the definition of "economic efficiency"? Or maybe it's just me. Well, I don't want to replace my job with my house so that it makes money for me and I never have to work again. If I finance a house with land and have paid it off after 30 years, it was economical for me. How much interest I have given away until then bothers me about as much as a sack of rice falling over in China. Because if I continue to sit in my apartment and throw the same money out of the window for 30 years, after 30 years I still will have neither land nor a home of my own. So, in comparison, I am doing quite well. That is economic efficiency for me. But I never addressed that; I only referred to my parents' photovoltaic system with the example from f-pNo. But he has now clarified that as well.

Let's come to the Kfw 40 Plus house (my project), with which I have monthly heating costs of 0.00€ (due to the air-to-water heat pump & ventilation, so only electricity) and depending on the season, on average about 20.00€ monthly electricity costs including heat pump & ventilation thanks to the 5.3 kWp PV system. After thirty years, my electricity price will increase somewhat. Provided I don't add something else. However, compared to others who are still 100% dependent on electricity and will probably pay ten times as much as today, I am better off. Or has electricity recently become cheaper?

But thank you for worrying about my uneconomical nature. Added to all this is, of course, the already mentioned luxury. Own garden, own barbecue area, own terrace, doing whatever you want. Like-minded builders of more or less the same age, where the children can integrate perfectly too. And and and...

It's a pity that the thread missed its goal.