Since our bathroom only has a small radiator due to space constraints and it does not provide enough power, we have hung an infrared heater above it. It takes 30-60 minutes and the bathroom is at 28 degrees or more.
Affordable is relative, depending on how intensively it is used. However, we are enthusiastic about the possibility and will later combine it with a suitable solar system. Then the costs should also be manageable.
It's best to get information at trade fairs in your area. :)