> There even was an official program to replace your old lightbulb for a new LED one for free

Wow do they still have incandescent lightbulbs? Mental.

That depends on what the source of your heating is.

Say, in Norway we largely use (hydro-) electric power for heating, anyway.

So, the 2% efficient (for lighting) incandescent bulb doubles as a 98% efficient space heater, utilizing the 2% loss to light said space. 100% efficient!