A turf maintenance vehicle includes an internal combustion engine and an energy converting device that converts mechanical energy from the engine to electric energy. The vehicle also includes at least one subsystem powered by the electric energy from the energy converting device. The vehicle further includes a demand sensor that detects electrical demand from the subsystem. Also, the vehicle includes a controller that changes a speed range of the engine based on the electrical demand, which changes the operating voltage range output from the energy converting device. A method of operation of the vehicle is also disclosed.