Good point - the comms satellites are not even "keeping" some of the energy, while a DC would. I _am_ now curious about the connection between bandwidth and wattage, but I'm willing to bet that less than 1% of the total energy dissipation on one of these DC satellites would be in the form of satellite-to-earth broadcast (keeping in mind that s2s broadcast would presumably be something of a wash).

I doubt half the power is to the transmitter, and radio efficiency is poor -- 20% might be a good starting point.

the majority is likely in radio waves and the inter satellite laser communication