If you didn't have too many accessories running off the "generator" motor, you will not have as much load or drag on the engine (the nitro engine I mean) powering the whole thing. Basically you will be bleeding off the amount power it takes to spin the electric motor itself (the mass of the armature inside, friction etc) and the power it takes to run any accessories. If you ever had a bicycle with one of those wheel mounted dynamos, then you'll remember, when you had it turn using the bike's wheel and your headlight turned on, it was much tougher to operate the bike; you had to pedal harder.