A hybrid drive train for a self propelled power trowel includes a frame having a centerline from front to rear, an engine-generator set, a pair of rotors with trowel blades tiltably connected to the frame and positioned to support the frame above a concrete surface being finished, electric motors for driving the rotors, means for tilting each rotor toward and away from the centerline, and means for tilting a rotor fore and aft, parallel to the centerline. A rectifier and inverter in series at the engine-generator output allows engine speed to be regulated by a capacitor bank, and usage of highly efficient brushless AC synchronous motors to drive the rotors. A rechargeable battery may be connected in parallel with the capacitor bank.