Fuel cell or operating costs, photovoltaics and solar thermal?

There are ovens also independent of room air with fresh air connection from outside and airtight doors.. Or with water connection, so that they can heat the heating water. But you have to look critically whether it is worth it, how often you are at home to party through, whether you need the room-side energy in some way...

Since the system temperatures are similar, this would fit: gas boiler + ST + water-bearing fireplace stove. Heat pump + photovoltaic also go well together, but that does not fit your design without underfloor heating.

I just looked at the data of the Viessmann fuel cell. that's only 1.1 kW thermal and 0.75 kW electrical. that's nothing. to speak of fuel cell heating is quite a stretch.

Well, with gas valve to I meant that it is no longer socially desired to heat with gas or that economically it might not make sense in maybe 20 years because gas has become brutally expensive.

Otherwise, the thing with natural gas is only partially true. That may be the case today, but there are already systems that convert the overproduced eco-wind power into hydrogen and store it instead of leaving it unused. This just doesn't happen on a large scale yet, which is why the industry gets its hydrogen from natural gas - but that will certainly change in the future.

As far as that goes, I am extremely tech-optimistic and always assume the best.

Otherwise, what you said about durability was exactly the right trigger:

"According to the manufacturer, maintenance is only necessary every five years. The fuel cell stack is therefore designed for a lifespan of 12 years, but the device as such can perform its function for up to 20 years."

Of course, I had completely wrong ideas there. I immediately assumed that the thing would be sitting in the basement for at least 20 years anyway.

If it were a new build, I would otherwise agree, just a heat pump + photovoltaic and that would be fine. But since it’s an old building and the ceiling height is only 2.45 meters, I actually didn’t want to install underfloor heating everywhere, as that again costs ceiling height.

I just looked at the data for the Viessmann fuel cell. It's only 1.1 kW thermal and 0.75 kW electric. That's nothing. To call that a fuel cell heating system is quite a stretch.

Yes?

"The fuel cell heating system is suitable for an annual heat demand of up to 32,000 kWh per year and an electricity demand of up to 6,200 kWh. The Vitovalor PT2 can produce a maximum of 18 kWh of electricity per day."

That sounded okay to me as a layperson. The two of us currently only consume 1,500 kWh in our 90 m² apartment, even though I work from home. And my grandparents used about 30,000 kWh of gas last year in that very house with the old gas boiler.
So I would have expected that it fits well enough. Otherwise, it must of course be said that there is always a condensing boiler next to it, meaning with the fuel cell, in case it’s not enough in winter. So it definitely doesn’t work completely without it here either.

in the technical data:

Electrical power
Fuel cell module: 0.75 kWel
Thermal power
Total power: 0.9 to 30.8 kW (Fuel cell module: 1.1 kW)

There is a gas heater built in right away, which is kindly taken into account in the performance data.

I am considering back and forth.

Proper insulation, careful planning of surface heating (underfloor heating, wall, ceiling, or radiators with high output). In addition, a compact, affordable, and easy-to-install/replace heat pump (not a split system) and as much photovoltaics as possible - that would be my approach. Take advantage of subsidies for the heat pump. It will never work without electricity, and that is all you need. The car will soon run on electricity as well. If economic efficiency is less important than being "green," then immediately get an energy storage system; otherwise, get it later.

might not make sense in maybe 20 years anymore, because gas has become brutally expensive.

1. Then you have heated for 20 years with one of the most economical systems ever.
2. Why should gas become "brutally" expensive by then? Nord Stream 2 will provide an additional 55 billion m³/a, MONACO about 17 billion m³/a. Supply is increasing faster than demand. The latter is mainly driven by the base-load combined cycle gas turbines to be built, which will replace coal and nuclear power. As long as the tax burden per m³ of gas does not increase exorbitantly, I currently see little indication that could cause a disproportionate increase in the gas price.