A hybrid powertrain includes a hybrid electro-mechanical transmission and a power source. A planetary gear set having a first, a second, and a third member connects the power source with a first and a second motor/generator. A battery is operatively connected to the motor/generators for receiving power therefrom and delivering power thereto. An input member rotates with the first member, the first motor/generator rotates with the second member, and the second motor/generator rotates with the output member. A first torque-transmitting mechanism is engagable to connect the second motor/generator for rotation with the third member. The battery and the second motor/generator provide an electric-only operating mode to power the output member when the first torque-transmitting mechanism is not engaged; the power source, planetary gear set and first motor/generator thereby being disconnected from the output member during the electric-only operating mode to prevent parasitic drag.