Dave wrote:
If a simple dipole is fed with 100 watts and radiates 95 watts, it is
95% efficient.

How are you measuring the antennas "output" or "radiated power?"
--and--
How much of that 95 watts is spent in heating the dielectrics and metal
(or is that "missing" 5 watts the heating power? And, how did you
measure that?)

JS