Geothermal heat pump or gas boiler - experiences?

...Actually want a geothermal heat pump but don’t know if it still works with the kfw55.

A geothermal heat pump with a ring trench collector only really makes sense if it is done during the excavation of the basement.
Subsequently, this can possibly also be done with a small excavator (<2t), but then an insane amount of excavation material has to be reshuffled.
For a deep drilling (vertical heat exchanger), the property must be accessible for heavy equipment.

A gas connection would already be there since an old house once stood there and the connections exist. But we also know that gas prices are rising quite a bit.

The electricity prices for the heat pump will then – possibly with some delay – also go up.

If you want to, then do it. The ground-source heat pump is theoretically the most efficient system. In practice, however, due to the costs, it is unfortunately not the most economical. The additional costs compared to an air-source heat pump will hardly be recouped, as houses today are too well insulated.

I would advise against gas. Political plans foresee the phase-out of fossil heating, regardless of the party. If you install a gas heating system now, you will most likely have to switch to a heat pump with the next heating system anyway. So it's better to install it the way you want from the start. How electricity and gas prices will develop in the long term cannot be predicted reliably at the moment. In the short term, electricity prices will certainly rise because we are currently filling the gaps from the nuclear and coal phase-out with gas power plants when wind and sun are not cooperating.

The others have already written it, for a 150m2 house I would invest in an air-water heat pump and photovoltaic, for 250m2 a ground-water heat pump, etc.

... for a 150m2 house I would invest in an air-water heat pump and photovoltaics, for 250m2 a ground-water heat pump, etc..

to translate all the abbreviations you already have to be familiar with them, and if you are familiar, you don’t need the tip anymore :rolleyes: What I find a bit lacking in all the advice: We all have to change our energy technology. Gas is significantly less favorable than a heat pump. The price for all of us – see for example Ahrweiler – is FAR higher ... yes, do the heat pump ... I am facing a similar decision, also hesitating because of the prices and am talking myself into it :cool:

I provide another opinion per heat pump (air-to-water heat pump). We even have a slightly oversized one. In the first full year in the house, we consumed about 2350 kWh. With 153 m², a cozy 24°C in winter, and a lot of hot water consumption. We come to heating costs of approximately €53 per month.

The price for all of us – see for example Ahrweiler – is FAR higher ...

The example is one of the worst that can be given. In the Ahr Valley there is a history of major floods that have repeatedly overshadowed the previous record from 2016, e.g. 1804 with a significantly higher flow than in 2021. There is even a separate Wikipedia page on floods in the Ahr Valley. The problem last summer was not climate change but the ignorance of history combined with the hubris of trying to derive models for extreme events from measurement series spanning only a few decades. And as a cherry on top, people didn’t believe their own short-term forecasts... because what cannot be must not be. Instead of seriously addressing the problem, electioneering is being carried out, and the state is now spending a lot of money to rebuild houses in the flood area... Just so no one here gets me wrong, I am absolutely in favor of not unnecessarily polluting (of any kind) the environment. You don’t need a good reason other than that it doesn’t belong there and we have no idea what the pollution really does. But I am absolutely against cheap electioneering with such disinformation and deciding on measures without considering reality. This leads to outcomes like shutting down nuclear and coal and filling the gaps with Russian gas. Or installing heat pumps in old buildings under heavy pressure, which then mainly run the electric heating element, powered by exactly that gas supply.