Pellets with solar thermal or photovoltaic?

I don't want an air heat pump because of electricity consumption in winter. I still consider it purely electric heating where I buy a lot of electricity in winter and it keeps getting more expensive. Sure, pellets will also get more expensive...

I would reconsider heat pumps if I were you. I think pellets are a mistake. By combining photovoltaic and heat pump, you can achieve zero heating AND electricity costs over 20 years through the subsidized feed-in tariff and good planning. Without a chimney and with low maintenance costs. And it doesn't look bad after the subsidy period either.

- I don't want an air heat pump because of electricity consumption in winter. I still consider it purely electric heating where I buy a lot of electricity in winter, and it keeps getting more expensive. Of course, pellets will also get more expensive...

That's why people use air-water heat pumps. They are now even profitable in older buildings. In new buildings (together with geothermal heat pumps) currently state-of-the-art.

Air water heat pump .... is such a heating system initially so much cheaper than the pellet heating.
Is there a comparative calculation here with the current energy costs

The basement room will be built no matter what goes in, if the heating in that room is smaller then another basement room will simply be larger. So no cost difference.

In summer I don't want to heat with pellets at all but only generate heat through solar support. So no costs incurred.
Here solar thermal would be more efficient. Photovoltaics, however, are more flexible if the storage is full.

If you don't care how many of your square meters (at €2000 each) are not usable for you, then of course you can ignore that in the calculation...

And just for the costs of the chimney sweep, you have already heated until March...

The basement room will be built no matter what goes in it; if the heating in that room turns out smaller, then another basement room will simply be larger. So cost-wise, no difference.

Well, the argument is nonsense, like "I build 5 rooms no matter what, but one I will not use and just lock the door."

An air-to-water heat pump doesn't have to be much cheaper than the pellet heating, a few thousand forward temperature. That having too high electricity costs in winter and a direct electric heating is of course nonsense, otherwise, the heating system wouldn't exist. Do you have a water protection area? Otherwise, with a high groundwater level, a flat collector for geothermal energy is excellently suitable.

Air water heat pump .... such a heating system is so much cheaper to purchase than the pellet heating system. Are there any comparative calculations with the current energy costs?

Energy costs: with a heat pump, you get 4-5 kWh of heat from 1 kWh of electricity without further system losses through storage, pumps, chimney. There are almost no maintenance costs and no chimney sweep. Electricity is getting greener every year, and politically it looks like electricity will be wanted in the future. A part (20-40%) of the electricity can come from your own roof.

With a heat pump, there is more own contribution and savings potential. Whether you can use that is an individual question. So potentially yes: a heat pump can be significantly cheaper.