Oil out, gas condensing boiler + solar in?

No, no underfloor heating

Without underfloor heating, don’t worry about the heat pump. It will be too expensive because the annual performance factor is far too high. Maybe feasible with replacement of all radiators by oversized low-temperature convectors at 40/30 °C, but still significantly more expensive than your oil or new gas.

Then you should be aware that this applies equally to solar thermal

Well, that is somewhat different. Photovoltaics without a ridiculously expensive battery can only be used with exact simultaneity of demand and generation. Hot water can be stored cheaply and used in the evening hours or mornings. Solar thermal can be well used for heating support in the transitional phases. On south-facing roofs also on sunny winter days, but here only to a limited extent.

Heating costs of "0€" can only be achieved if the 6-10k euros for the photovoltaic system are not included.

The solar thermal system on the existing roof with heating support also receives good subsidies: 2000€ base + 500€ if a new heating system is purchased at the same time + 10% KfW subsidy + possibly municipal or state bank subsidies.

The future belongs to electricity

Oh really. We still have a well-developed, full, functioning gas network. Soon with an additional NordStream2 pipeline and the US empire also wants to build LNG terminals financed by European gas customers. That does not smell like gas will stop coming anytime soon. Price-wise, the gas price is also more predictable than electricity. The latter changes its price yearly due to political decisions much more strongly than gas. And in existing buildings without underfloor heating, heat pumps will not achieve reasonable annual performance factors in the next 15 years either, and electricity will definitely not get cheaper!

Alternatives from an ecological perspective: Gas-based fuel cell. Also generates electricity, but only a few hundred watts. You have a very high self-consumption rate. Also heavily subsidized by KfW bank. Pellet stove, also with BAFA subsidies, and the space that oil tanks currently need will then be needed for the pellets. But they are ecologically questionable, like many things in mass production (pellets from Hungary = Carpathian primeval forests, or shipped from Canada, for example). Wood log gasifier boiler. Also plenty of subsidies and clearly superior to any fireplace stove in combustion and emissions. Especially worthwhile if you get cheap wood, but also not bad for normal customers. Definitely local fuel sourcing possible.

In terms of price, the gas price is also more predictable than electricity. The latter changes its price significantly more annually due to political decisions than gas.

I admit, I haven't checked it against statistics now, but still: WHAT?!

Does the supply temperature apply to the last 10 years, in the previous decade the gas price increased by 50% in a few years. Neither is predictable.

Thank you very much in the meantime for the many useful ideas.

I might actually consult an independent energy advisor. Actually, when looking at the house and the electricity and heating oil consumption, one should come to a clear conclusion. And if the conclusion is that everything stays as it is for now, that suits me just fine.

I also find fuel cells interesting; I have already made many films about them. It could even cover my basic consumption, but you have to keep in mind that at some point the stack needs to be replaced.

Matthias