Sorry Max. I do bow to your superior knowledge. I should have clarified, and do so later in the piece, and Tesla acknowledges in his patent, that most of the energy input will come from steam or compressed air. What I should ahve made clear is that the generator might use 1kW for excitation - ie field coils - from a 10KW output. Not to be confused with the excitation in the plans, which is a spark gap intended to get non-technical viewers excited I think!
@David: You say "Maybe Tesla did produce a generator that gave 10KW output for a 1KW excitation input, giving it 90% efficiency electricity wise..."
Hang on, 90% efficient? If you put 10 in and get 1 out, you are 1/10 = 10% efficient, so if you put 1 in and get 10 out, that means you are 10X or 1000% efficient (which is pretty damned efficient, let me tell you -- I R an Engineer and I know these things :-)