Construction costs are currently skyrocketing

And after four years of the traffic light coalition, they are popularly blamed for everything.

They were already blamed for everything one day after taking office :) But that is probably part of the fate of politics.

One thing is the professionally meaningful aspect, and here the "training" to become an energy consultant is rather nonsense (it is a 2-day IHK course + exam for 2,500 EUR), but with a good energy consultant you can definitely get a lot out of it. Especially in the case of renovating old buildings, good energy consultants are worth their weight in gold. The other thing is the rules and regulations. I have not familiarized myself with them. At that time, it was also rather clear to me that I would build according to the energy saving ordinance, but more because I was wrongly advised by a financial advisor. With today's knowledge, I might have at least built to KfW 55 standards.

I can confirm that for my husband and me. We only built according to the Energy Saving Ordinance (i.e. the superficially cheapest option) because we didn’t understand all the subsidies, applications, etc., even though, according to some forum members, it would have been easy to make our house a KfW 55. But spending several thousand euros just for the energy consultant (I know that a part of it is reimbursed) discouraged us. Sometimes I wondered whether it could be done more easily or if the matter is really so complex that you need a specially trained energy consultant.

Right, it is complicated. The necessary paperwork was about 5 cm thick due to required order confirmations and invoices! The energy consultant was required anyway for some subsidies. I received subsidies for geothermal heat pump drilling (5€ per meter = 550€), passive house (3000€ per residential unit via Progress NRW = 6K), BAFA (about 17K € for heat pump + controlled residential ventilation), KfW (60K for 2 residential units due to KfW40+), subsidies for battery (about 700€) and 2 wallboxes (over 2K). I probably forgot to mention something (and I actually forgot (rather overlooked) to submit an application on time and thus lost about 700€ for the battery subsidy).

At least the topic of energy consultants was streamlined this year ;) I also find bureaucracy tiring not only with RE or funding... the utility connections involve a lot of paperwork as well

My statement did not refer to VAT either - that is only a pass-through item.

And yes, it is relevant because I generate about €200 of taxable profit each year and have to pay taxes on it - but not anymore starting next year.

That makes sense that way! The observation period for hobby activities ranges from 7 to 15 years depending on the case. I was indeed not aware of the 20 years for photovoltaics. Due to the current price and supply situation, I have not dealt intensively with the tax aspects anymore ;)

right, that is complicated.

I cannot confirm that. Our general contractor informed the energy consultant working with him that we want to build according to kfw55, and he then set everything in motion. Only now and then did I receive something for signature or some documents. We had to submit an application for the funding at Kfw and now have two financings, but the financing agent took care of that.
Sure, a bit of additional effort, but nothing dramatic.