ᐅ Heat pump and photovoltaic system despite oil heating from 2019?

Hello everyone,

we are planning to purchase a semi-detached house for personal use. The property dates from the 1950s and requires extensive renovation. Energy efficiency rating H, primary energy demand around 350, final energy demand about 300.
The only positive aspect is the oil condensing boiler from 2019. The oil tanks date back to 1990.
Since I am planning comprehensive renovations (external insulation, basement ceiling and wall insulation, new triple-glazed windows, electrical wiring, etc.), I am considering replacing the heating system as well. Currently, there are good subsidized loans available from KfW for this, so I am leaning towards a heat pump. I often read that installing a photovoltaic system at the same time is recommended. We plan to install underfloor heating, and otherwise, I intend to arrange conventional construction financing through a bank, which would give me more flexibility regarding trades and contractors.

Now, the following questions:
- Is underfloor heating compatible with the existing boiler?
- Should we keep the oil heating system or switch to a heat pump?
- If we choose a heat pump, should we also install a photovoltaic system?

Thank you.

Regardless of the heating system, fully cover the roof with photovoltaic panels.

Ah, I forgot to mention: there are extension options under Section 34 of the building regulations, so an additional storey is possible. However, since we currently have no need for it (no children, saving costs, etc.), we decided to forgo this. Maybe in 5-10 years – would it then be possible to remove the photovoltaic system and reinstall it on the new roof? At the moment, it is a single-pitched 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 usually overcast and gray. Photovoltaic panels are a nice bonus but not a requirement. However, with a reasonable offer, photovoltaic is the only part of the house that actually generates money instead of costing it. Reinstalling the system on a new roof is not a big problem. Therefore, I wouldn’t let the theoretical possibility of adding an additional storey stop me.

If you are renovating everything anyway, the current condition of the house is less important than the desired condition. In that case, a complete renovation is basically equivalent to a new build.