Oil out, gas condensing boiler + solar in?

No, no underfloor heating. I was never a fan of that. And with deep drilling, supposedly some bad things have happened already...

Matthias

I have never thought about heat pumps + photovoltaics before because I always see the fundamental problem that I mainly have electricity when I don't need heating anyway. In winter, when I need heating, I hardly have any photovoltaic electricity. Rather doubtful to me...

Then you should be aware that the same applies to solar thermal ;)

Both are rather a small extra income during the transitional period or on a single, really sunny day. Unless the photovoltaic system is properly large, at 20+kWp you can get a decent amount.

But in summer you have plenty of electricity to use or sell with photovoltaics. With solar thermal you have plenty of hot water. What do you do with that?

And with deep drilling, some bad things are said to have happened...

Matthias

I'm just wondering - what bad things could have happened there?

It can't be a permanent solution to burn heating oil...

It also can't be a solution to invest now unnecessarily in outdated technology and start burning gas for the few percent savings. If you're only concerned about the CO2 balance (on paper), you could also burn pellets. However, the one-time purchase also costs CO2 and resources.

The future belongs to electricity. I would stick with oil for now and renovate the house energetically in the long term to eventually be able to operate a heat pump sensibly. They are getting better and better.

Is there anywhere an online calculator where you can roughly estimate how much gas I would consume with a modern condensing boiler combined with solar support if I currently use about ten liters of heating oil per square meter per year?

I think you would do well with an energy certificate in order to have data that can be used.

Economically as well as ecologically, I consider it the wrong idea to replace something that is working.

I have never thought about heat pumps + photovoltaics before because I always see the fundamental problem that I have the electricity mainly when I don't need heating anyway. In winter, when I need heating, I hardly have any photovoltaic electricity. For me, rather

Yes, you're not wrong, but the electricity in summer doesn't get lost; instead, it is fed into the grid and compensated for. With the profit, you then buy electricity again in winter. I thus have about €0 heating costs.