Toyota debuted the new Prius (2010 US model year) at the January 2009 North American International Auto Show, and sales began in Japan on May 18, 2009. Toyota cut the price of the Prius from ¥2.331 million to ¥2.05 million to better compete with the Honda Insight, leading some to wonder whether increased sales of the Prius might come at the expense of sales of other vehicles with higher margins. Competition from lower priced hybrids, such as the Honda Insight, also made it difficult for Toyota to capitalize on the Prius’s success. As of June 2013, Toyota has sold about 1,688,000 third-generation Priuses worldwide.
At its introduction in 2009, it won the Car of the Year Japan Award for the second time.
Its new body design is more aerodynamic, with a reduced drag coefficient of Cd=0.25. This figure is disputed by General Motors which found the value for the model with 17-inch wheels to be around 0.30 based on tests in GM, Ford, and Chrysler wind tunnels. Car & Driver measured the 3rd Generation Prius at 0.26 in a privately arranged 5-way wind-tunnel test of comparable cars. An underbody rear fin helps stabilize the vehicle at higher speeds.
The estimated fuel-efficiency rating, using the U.S. EPA combined cycle, is 50 mpg-US (4.7 L/100 km; 60 mpg-imp). The Prius was the most efficient car powered by liquid fuel available in the U.S. in 2009, based on the official rating. Only the first-generation Honda Insight (2000–2006) equipped with a manual transmission attained a lower fuel consumption rate. The official UK fuel efficiency data for the Prius T3 is Urban 72.4 mpg-imp (3.90 L/100 km; 60.3 mpg-US), Extra Urban 76.4 mpg-imp (3.70 L/100 km; 63.6 mpg-US), Combined 72.4 mpg-imp (3.90 L/100 km; 60.3 mpg-US).
The 1.8-liter gasoline engine (previously 1.5 liters) generates 98 hp (73 kW), and with the added power of the electric motor generates a total of 134 hp (100 kW) (previously 110 hp or 82 kW). The larger engine displacement allows for increased torque, reducing engine speeds (RPM), which improves fuel economy at highway speeds. Thanks to its electric water pump, the Prius engine is the first consumer automotive production engine that requires no accessory belts, which also further improves its fuel economy. The electric motors and other components of the hybrid powertrain are also smaller and more efficient than the industry average. Toyota estimates the new inverter, motor and transaxle are 20 percent lighter.