Flat collector vs tube collector

I determine the performance experimentally over several days (clear, cloudy, dull, cold) and see which hot water temperatures I achieve. I can then extrapolate this to a large system on the roof area to decide whether I want to put up with it. This results in the core question of the thread opening: flat plate or tube.

That sounds more like a hobby and an activity to me. That’s okay, fine to do – but I wouldn’t argue with profitability, as that quickly puts you on the sidelines in discussions.

In the forum I mentioned, you’ll surely find someone who knows about the different tubes.

Alternative project suggestion for you: heat the water barrel using electricity from guerrilla photovoltaics (and later install the proper photovoltaic system ;-))

O.K. I had already done the photovoltaic calculation a few years ago; maybe something has changed in the meantime. One of the problems back then was that for price reasons, I only wanted to buy the parts and assemble them myself, which caused the subsidy to fail, making the planned payback periods obsolete. I will update myself on photovoltaic systems. Thanks for the tip about the water container :-) I can already see myself sitting in the garden in a clay pot, waiting for a thunderstorm to convert lightning amps into warm water with a kite string like Franklin once did. ;-) My skepticism also stems from the experiences of other acquaintances who found that the promised results were not met. For example, there were corrosion defects in the pipes that are to be prevented in the future with electronic potential compensators (current). Oxygen-binding agents are now also supposed to be added, which must be analytically controlled (additional maintenance effort). One can definitely get "something on the heels." From my own experience with electricity, I can say – here in Berlin, the meters are partially being replaced with digital ones so that operators can soon read them remotely via the telephone line. As part of this, not only the meter is replaced, but the distribution must be retrofitted according to the new DIN standards. Additional surge protection circuit breakers for network protection, adaptations for the future internet connection of the digital meter. If the earth current values are not correct, additional earthing crosses must be installed. So much for surprises that arise when connecting to the electricity grid. (Costs, costs, ...) ...and I have to do that if I want to sell the "self-generated" electricity. Of course, I do not want to change my life rhythm and start the washing machine at noon via a timer when the sun is at its highest—that is not so pleasant for me either. My machine only runs when I am there! ..... ever had water damage? Thanks for the forum tip; I will get informed there about my DIY project. If it is worthwhile, I will report. My heating is still running now, and I shower without thinking about it. When it gets warmer soon (climate change? we've never had it this warm before), I will turn it off, and then the electricity meter will start to ring. It would be nice if the sun could help a bit. Is showering less actually recommended also from the payback perspective? ;-) Greetings from the still showering "clean man."

Yes, have another look at photovoltaics, the opinions presented here are well-founded, without self-interest, and from critical builders with their own experiences – collective intelligence and all that.

By the way, my reference to guerrilla photovoltaics was meant seriously, less so the part about heating water, but just google it. Meant as a DIY project, like ST only smaller and with electricity :)

Yes, and please report back, we are curious.

Is showering less actually also advisable from the perspective of amortization? ;-)

That was a good one :)

I have no idea about photovoltaics. But I can say without lying that since 14.2. our ST system has been making the hot water alone without additional heating, I have turned off the heating for hot water. The position of the sun is already sufficient and will be sufficient until about mid-October. Hot water for two. Not so bad at all. Karsten

since 14.2. our ST system alone produces the hot water without additional heating

The ST system is already sufficient. You won't get more yield in summer when the sun really shines. With photovoltaics, yes (even a bit in winter), which you can then sell. The OP doesn't understand that.