Counterintuitively, they are best mounted on ceilings in commonly-occupied places, radiating heat downward. They heat the objects and people in the room, and the air mostly indirectly. The infrared light/heat bouncing around the room means you can be comfortable at an ambient air temperature about 5C lower than with traditional heating. They're common in infrared saunas and hot yoga studios, but new to the home heating market. I haven't had a full winter with mine yet, but claims of savings on the order of 40% are common.
These are more efficient and far less costly to install than radiant floor heating systems... several hundred euros per panel, plus installation.
Before you consider any heating system, however, know the differences among radiant, convective and conductive heat transfer!
For bonus points, combine with renewably-sourced electricity and other home energy loss minimizations.