[ckilmer]

The EM Drive uses energy in that it runs on electricity. It does not produce energy.
.................
does it use as much energy as it produces?

[Rockingham]

Like the electric motor on a Tesla, the EM drive uses electric energy but does not produce it. Where a Tesla motor converts electric energy into mechanical energy to turn the wheels and propel the car, the EM Drive on a spacecraft -- if it works -- converts electric energy into thrust to propel the spacecraft.

Precisely how the EM Drive could do that is disputed, with the lack of a reaction mass being expelled as hot gas from rocket nozzles on the spacecraft seen as a violation of the law of conservation of momentum. This objection need not be fatal because nature's rule book is like a bad contract, with all sorts of exceptions, loopholes, and tricks for the clever to discover and exploit. Perhaps the EM Drive is just such a trick.