What is the name of Toyota's hybrid drivetrain system?

Toyota’s hybrid drivetrain system is called Hybrid Synergy Drive.

Usually abbreviated HSD, the system combines a gasoline engine with electric motor-generators and a planetary power-split device. Instead of relying on a conventional stepped gearbox, it manages engine speed and power flow electronically and mechanically, allowing the vehicle to blend gasoline and electric propulsion smoothly.

Toyota first used the system’s basic architecture in the original Prius, introduced in 1997. HSD later spread through Toyota’s hybrid range and into Lexus models. Depending on the vehicle, the system can drive the wheels with the engine, electric motors, or both, while regenerative braking recovers energy that would otherwise become heat.

“e-CVT” is a frequent source of confusion. It describes the continuously variable driving behavior of Toyota’s hybrid transmission, but it is not the branded name of the complete drivetrain. “Power Split” describes the operating principle, while Hybrid Synergy Drive is the canonical Toyota name historically used for the system. Toyota has also introduced newer hybrid-system terminology for some current generations.