[amluto]

The numbers are easy to run, and the added power consumption is no joke. It’s even worse if your heat pump fails to achieve Carnot efficiency. Never mind that heat pumps can be heavy and may be completely destroyed by even a tiny micrometeoroid strike.

[pfdietz]

Yes, it needs more solar power. But solar panels should be much lighter than radiators, potentially vastly lighter. Even if Carnot efficiency is not approached there is plenty of room for improvement in the size of the radiators.