New building with granny flat: Photovoltaic - Electricity - Heating

No problem for me, they are parents.

I have always allocated based on m2 of living space. That's how my tax software requires it. There has never been a problem.

and what electricity costs do you then apply for heating if you don't pay for the electricity? or have paid once through the investment in solar. Of course, with oil, gas or district heating, it is simple

and what electricity costs do you then assume for heating if you don't pay anything for electricity? or have paid once through the investment in solar. Of course, with oil, gas or district heating it is simple

I should give that some thought. Thanks for the hint. I don't have an electricity meter for the granny flat.

Thank you very much for the many useful tips. There was a lot that I hadn’t even thought of. As I said, the mother-in-law is still living in the [Einliegerwohnung] for the time being. That shouldn’t cause much stress. And later, before concluding a contract with the tenant, one must agree on the conditions.

I think that the heating costs with photovoltaic and heat pump are generally lower than those of normal rental buildings with gas heating, no matter how roughly you calculate it. We don’t intend to make a profit from the heating costs either. And with a small [Einliegerwohnung], we’re not talking about huge sums. If in the end it’s not settled down to the last euro, it should simply not matter to the tenant. You just have to be sure that you are acting according to the applicable law and don’t get into trouble with the tax office.

I do have an electricity meter at the WP. I can then allocate the electricity consumption to the m2. That should be sufficient for the [FA]. I will do it that way next year.