Purchase decision small semi-detached house 100 sqm from 1930

Topic heating: Does it make sense to initially continue operating the heating with low-temperature radiators and underfloor heating in connection with the oil heating, then with a lower flow temperature – and then later simply replace the oil heating with a heat pump? Or put differently, is that even possible?

Currently, it is difficult to get a heat pump at all. The idea would be to simply replace the oil heating with it later, once the market has calmed down again.

Maybe one more thing regarding heating: we are currently facing similar decisions and recently had a conversation on site with our plumbing company. First of all, they were surprised at our low consumption, even though hot water is also gas-powered here (on average over the last 5 years with 4 people around 10,500 kWh/year). Then they said that a new heating system actually doesn't make sense because we consume so little and the heating system would still run well for many years. He now wants to offer us a hybrid solution first and then a complete solution. In the attic and 1st floor, it would remain with new radiators, and on the ground floor we would combine it with underfloor heating. He also said that he thinks everything will calm down towards the end of the year. From his point of view, there have been multiple orders/panic buying and that's why the shortage occurred. We will postpone the whole thing to next year and then see. Basically, he said that a new heating system actually doesn't make sense and we should rather just carry out the remaining energy measures. And wait until everything calms down. If only one had a crystal ball...

5 years with 4 people around 10,500 kWh/a)

What exactly does that mean in numbers (€) all inclusive (contract/consumption/maintenance…) 2021, current and future? And what is the equivalent to oil and heat pump (JAZ4)?

What supply temperatures are used in winter?