Lol! My point was to run the 100 wifi routers on electricity. Yeah, I know the electric bill would go up. Still, was my math correct? I think I shorted by a 1000 fold. What say you? My office router is about 75 degrees by feel.
Love engineers who have built the world, unlike theoretical physicists who spend their day on white boards thinking they have the Universe figured out. String Theory is defunct; dark matter and dark energy are still a math problem they can't work out - all speculation. Engineers build stuff.
There is another factor. A WiFi node has an antenna with some “gain”. The gain presents energy to the intended coverage area and limits energy to areas where coverage isn’t needed. It is analyzed as if the “effective isotropically radiated power” were “real” but in actuality a 20mW transmitter through a 10dbi antenna “acts” like a point radiating antenna fed with 200mW to someone in the intended coverage area. A WiFi node can’t produce heat in excess of its actual power output.
So in your case, we would need more info about the level of heat you wanted to achieve, factor in Rf power required to generate that much heat, taking into account RF energy that escapes the room.
Just buy a heating pad.....