OK, but what about the rest of the price difference? Once the electrical is taken care of it should just be a matter of replacing the furnace and pulling some tubes and wires to the outer unit? You said 40k, but the heat pump itself isn’t even 10k.
German article, but some translation tool might help: https://www.tagesschau.de/wirtschaft/verbraucher/waermepumpe...
But there are other factors as well. Air to Air heatpumps are uncommon in Germany, we usually install Air to Water ones, which are more complex. Unlike other countries, our heat pumps are usually mounted on a concrete slab and not on the wall. Then there are some norms for quality of the water, etc. they aim to increase the lifespan of the system, but increase upfront costs
And why do subsidies INCREASE the price in Germany compared to Sweden?