New heat pump for old buildings without renovation

No. The decisive factor is always the supply temperature. Set all thermostat valves to 5 and lower the supply temperature until it is just comfortable in the reference room (usually the bathroom, as higher temperatures are desired here). Check the radiators to see if they are warm throughout. If one or more radiators are warm at the top and cold at the bottom, a hydraulic balancing must be carried out. To be able to operate at lower supply temperatures, the heat emission area is crucial. This means that the larger the radiators, the lower the supply temperature can be. Replacing the heating system with a heat pump therefore makes sense together with low-temperature radiators.

That is described too little. There are heating value boilers which, due to control reasons, do not go lower than e.g. 50 degrees as boiler temperature. Provided no mixer is installed, the minimum flow temperature is usually also at 50 degrees. That then makes it difficult.

That's true, but the regulation doesn't allow that anyway. You just get an indication of whether you can/could lower the flow temperature further.

For all those who are considering installing a heat pump in an old building.

Panasonic is launching a high-temperature heat pump in spring 2023 that can still deliver a flow temperature of 75 degrees even at an outside temperature of -10 degrees. An SCOP of up to 5.2 is mentioned. Thus, it is an alternative to oil and gas heating without having to switch directly to underfloor heating and/or insulation.

There is (still) no detailed information about the Aquarea L, it is yet to come.

A friend works in the industry and was traveling internationally a lot during the summer and spoke with people from the industry. He advised us (old building) to wait with the heat pump because some things for old buildings are supposed to happen in the near future. This matches your report. I am curious about what will specifically come onto the market then. The current heat pumps would require extensive remodeling here and cost a crazy amount of money, which is why we are moving away from it again; this investment probably would never pay off.

I would also first wait and see what will happen on the political side. Subsidies, possibly a cap on the heat pump tariff, etc. Then a hybrid system often pays off as well. It's just like always a matter of calculation...

Why not simply use air/air instead of operating inefficient radiators with high flow temperatures?