Toyota Motor Corp. executives on June 30, 1995, approve the development of a production hybrid vehicle -- code-named "890T" -- powered by what became the Toyota Hybrid System that combined an internal combustion engine with an electric motor.
Internal discussions at Toyota aimed at developing a vehicle for the 21st century intensified in 1993.
With engine advances a primary goal, the G21 Project (G for global and 21 for 21st century) initially set a target of raising fuel-efficiency performance to 1.5 times the level of conventional motors. However, Akihiro Wada, Toyota's executive vice president for R&D, ordered a two-fold improvement.
By the summer of 1994, the basic G21 concept was approved, but it was not until a year later that the hybrid approach gained momentum. Toyota engineers endorsed a hybrid format for the concept because a hybrid offered the prospect of doubling fuel efficiency.
From fall 1994, when development of the concept vehicle began, and into the winter, another major change occurred at Toyota when officials decided to adopt a hybrid system for the production version as well.
The automaker's early hybrid concept used a capacitor to store electrical energy rather than the battery pack that eventually became part of the production model's primary hybrid system, and remains a key part of Toyota's Hybrid Synergy Drive system.
The energy management system on the concept consisted of a 1.5-liter direct-injection gasoline engine, a belt-driven continuously variable transmission, an induction motor/generator and a power capacitor that temporarily stores electrical energy.
In addition to improving powertrain efficiency, the system enhanced fuel economy by regenerating energy and stopping the engine while the car was stationary. Toyota targeted fuel-economy levels double that of other vehicles in its class.
By the end of 1994, the project team had designed a hybrid concept car and coined the name Prius, and they had roughly a year to deliver it in time for the Frankfurt and Tokyo auto shows in 1995.
The Prius went on sale in Japan in December 1997.