Depending on the income situation, one could also reduce the buffer to zero for a few months and start saving again. Otherwise, ask the bank completely open-mindedly.
Since the operation of a photovoltaic system with surplus feed-in always constitutes an independent activity, of course all costs can be claimed as business expenses.
Thanks already for the tips. Basically, the financing is not tight, so we could still increase the monthly repayment or the installment a bit. I'll just ask the bank now, let's see what conditions they offer.
So the bank is currently offering us to simply increase one of the existing financing components by the corresponding amount under the same conditions.
Alternatively, I have also requested an additional loan that is explicitly allocated to the photovoltaic system.
Otherwise, I am afraid the tax office will cause problems later if I want to deduct the interest for the photovoltaic system that is included in the regular construction financing? Or is it unproblematic if the loan for the photovoltaic system is part of the general construction financing?