Air-water heat pump functional heating - Is this heating system prone to issues?

Hello, we received a supplementary offer from our heating engineer to carry out the heating program for the underfloor heating and screed drying with a mobile 20kw electric heater. Allegedly, the air-water heat pump cannot do this because it only has 8kW and if it would work anyway, something would surely break. Of course, I would like to save the additional costs, I think that 45 degrees flow temperature should also be possible for a short time with an air-water heat pump.

Have you done functional heating with the air-water heat pump? Is the heating element in the air-water heat pump really that susceptible?

Thank you!

Nonsense. Of course that is possible. But under certain circumstances not even possible. Why should the heat pump not be able to achieve 45 degrees flow temperature at +10 degrees outside? Sure, it becomes inefficient, but that doesn't matter for the short time. If the heat pump can't achieve 45 flow temperature at +10, it won't achieve 25 flow temperature at -10 either. And that's probably unlikely.

We also did it with an air-to-water heat pump. It was no problem at all.

Thank you for the answers. I spoke with the heating engineer again and we are now also doing the functional heating via the air-water heat pump. He also checked again with the manufacturer, and they apparently saw no problem.

Everything is more efficient than burning electricity 1:1 directly. If it were really cold outside right now, one might even warn against the freezing of the outdoor unit, but otherwise: fire away :)