Heating decision: air-to-air or air-to-water heat pump

Where does "whole roof" not make sense?

The price actually always decreases with larger systems. You only need one scaffolding, (usually) only one inverter, one installation, etc. Therefore, it is very, very rare to stop at half!

1. There were also limit values that massively affected the yield, and in the business case there was a sharp jump at, for example, 10kWp. 2. There were also subsidies that were capped. Also here: think carefully whether to take 10kWp or 30 right away; there was nothing in between. 3. If the money runs out at 10kWp, the money is gone and it is not always sensible to take out a loan for "whole roof" then. 4. It very much depends on the goal. If the goal is return, "whole roof" makes sense. If the goal is meaningful self-sufficiency, it looks different. Then the self-sufficiency benefit of the additional 20kWp is rather marginal. Being more than 100% self-sufficient is simply not possible. Feed-in, sure, but there are different people with different goals. 5. I just simulated it. My east-west system provides me with excellent self-consumption for eight or nine months because it starts up early in the morning and shuts down late in the evening. But in winter the angle hits mercilessly and winter-optimized south panels are clearly the smarter option. Also here: this is certainly not for the return chaser but for the person who is happy about significantly improved self-sufficiency in winter.

1. There were also limits that massively affected the yield, and in the business case there was a sharp jump at, for example, 10kWP. 2. There were also subsidies that were capped. Again, think carefully whether to take 10kWP or just 30, there was nothing in between. 3. When the money runs out at 10kWP, the money is gone, and it is not always sensible to then take out a loan for a "full roof." 4. It very much depends on the goal. If the goal is profit, a full roof makes sense. If the goal is reasonable self-sufficiency, it looks different. Then the self-sufficiency benefit from the additional 20kWP is rather marginal. You simply cannot be more than 100% self-sufficient. Feeding in, of course, but there are different people with different goals. 5. I simply simulated it. My east-west system provides me with great self-supply for eight or nine months because it starts early in the morning and stops late in the evening. But in winter, the angle hits mercilessly, and then winter-optimized south panels are clearly the smarter option. Again, this is certainly nothing for the profit hunter but for the person who appreciates significantly improved winter self-sufficiency.

1. 2. not relevant, as they are history. 3. Can be easily solved with loans. 4. What exactly is supposed to be “reasonable self-sufficiency”? Sounds not reasonable. The goal is either profit -> full roof or environmental protection -> also full roof 5. Either it pays off or it does not; that has nothing to do with “reasonable or senseless summer and winter self-sufficiency.” Simulating and calculating, of course, always makes sense!

1. 2. not relevant because they are in the past. 3. Can be easily solved with loans. 4. What is supposed to be a "reasonable autarky"? Sounds not reasonable. The goal is either return -> full roof or environmental protection -> also full roof 5. Either it pays off or it doesn’t, this has nothing to do with "reasonable or unreasonable summer and winter autarky" Simulating and calculating always makes sense, of course!

1 and 2 are absolutely relevant for an existing system 3 is easy to say, but I remember the mega stress I had with my KfW loan. My wife was about to give up the whole photovoltaic story. So: loan yes/no is not just a simple thing. 4 What is so difficult to understand about the term autarky? In summer no problem, in spring and autumn it depends on weather and yield. The days when a 10 kWp is no longer enough but a 30 kWp is enough are few. That is a goal that you simply do not consider, but that does exist. 5. see 4, for you only return matters. No problem, that is a valid goal and for that, as I wrote, full roof is absolutely reasonable. Different people, different goals, different solutions.

Where does a full roof not make sense?

We have a 40° roof pitch and almost exactly north and south orientation. I'm not completely sure yet, but from everything I've been told, covering the north side would probably also be more of a passion project. :/

Have a 40° roof pitch and almost exactly oriented to the north and south. I'm not sure yet, but from everything I've been told, covering the north side would probably be more of a hobby. :/

Yes, it's clear that some roof sides don't make sense, and areas can also be excluded due to trees or other shading.

But something like "meaningful self-sufficiency" and no money because loans are too complicated and therefore the wife stops the project is rather "interesting" than sensible.

But something like "meaningful self-sufficiency" and no money because loans are too complicated and that's why the woman stops the project is rather "interesting" than sensible.

That's called the reality of other people.