Heat pump and photovoltaic despite oil heating from 2019?

Hello everyone,

we are planning to acquire a semi-detached house for our own use. The property dates from the 1950s and requires extensive renovations. Energy efficiency class H, primary energy demand about 350, final energy demand about 300. The only positive aspect is the oil condensing boiler from 2019. Oil tanks are from 1990. Since I am planning extensive renovations (external insulation, basement ceiling/wall insulation, new triple-glazed windows, electrical work, etc.), I am considering replacing the heating system as well. As there are currently good subsidized loans available from KfW for this, I am planning to go for a heat pump… I often read that a photovoltaic system is recommended at the same time. We plan to install underfloor heating and otherwise I wanted to take out a regular construction loan through the bank so that I have more "freedoms" regarding trades, etc.

Now the following questions:
- Is underfloor heating possible with the boiler?
- Should we keep the oil heating or rather switch to a heat pump?
- If heat pump, then also a photovoltaic system?

Thank you.

Regardless of the heating, fully cover the roof with photovoltaics.

Ah forgot to mention: There are expansion possibilities according to [34 Bauordnung], so an extension is possible. However, since we currently have no need (no children, saving costs, etc.), we wanted to forgo this. Possibly in 5-10 years - could the photovoltaic system then be dismantled and mounted on the new roof? Currently, it is a shed roof; after the extension, it would be a gable roof.

When you need the heat pump the most, the days are short, the sun is low, and it is mostly dull and gray. Photovoltaics are a nice extra, but not a prerequisite. However, photovoltaics are the only part of the house that earns money instead of costing it with a reasonable offer. Reinstalling the system on a new roof is not a big problem. In this respect, I would not be deterred by the theoretical possibility of an extension.

If you are doing everything new anyway, the current state of the house is less important and much more the target state. And with a complete renovation, you end up with something on the scale of a new building.