Special case: a new building and a heating modernization

Hello everyone,

we have a special case:

We are being provided with a building plot by the parents-in-law.
An old house will be demolished and a new building will be constructed solidly according to the Energy Saving Ordinance standard (formerly KfW70).
Energy demand about 7KW (underfloor heating).

The parents-in-law's house is 20m away, the 25-year-old oil heating is causing problems and there is a solar thermal system with 3-4 panels installed (15 years old) (mostly radiators).
The old oil heating has 25KW.

In total, up to 6 residential units could be generated.

Now the question:
We would like to install a heating system together since both houses will remain in family ownership.

Which sensible modern heating technology is feasible?
Would a mini/micro combined heat and power plant make sense?

Conditions:
-We want to get away from oil
-no gas connection available
-Wood is relatively easy and inexpensive to obtain

I thank the experienced heating professionals for tips and suggestions

Best regards

Michael

You could calculate a wood gasification boiler. With a proper buffer tank with layers. There you could draw water at all required temperatures and integrate solar. Additionally, a hot water tank in the new building because of the 20m, otherwise it takes too long and circulation would be quite far and too many losses. Or hot water in the new building via Dlh, if there are only 2 of you. With underfloor heating, the heat loss of the pipe in the ground (PEX Duo pipe) is about 2-3W/m, so within limits. Combined heat and power plant without gas hardly possible, especially without oil.