Toyota shows off the redesigned 2010 Prius: more room, solar panels, and even better gas mileage

 The redesigned Toyota Prius offers incremental
 improvements to the best-selling hybrid.

In its first major update since 2004, Toyota's Prius hybrid is fully redesigned for the 2010 model year, with a fuel economy rating that increases to 50 miles per gallon in mixed driving and a solar-panel moonroof to help minimize air conditioner use.

Toyota unveiled the new Prius today at the Detroit Auto Show.

The Prius saves gas by including a battery that lets the vehicle run on electric power or with electric assistance in some circumstances with a  conventional gas engine that recharges the battery as needed, and powers the vehicle at higher spees and under hard acceleration.

Aerodynamics dictate the basic shape of the car, which stays the same as the existing Prius. However, as Toyota proudly points out, slight changes make the Prius the most aerodynamic mass-produced car, with a coefficient of drag of 0.25. 

Toyota also squeezed in more rear seat room, even as cramped rear quarters apparently represent one of the biggest problems with the new Honda Insight, the Prius's top competitor.

The Prius has become ubiquituos as a "green car," by supporters and detractors alike and is by far the best-selling hybrid vehicle, and Toyota has done little with the basic formula, choosing instead to offer more incremental improvements.

In addition to the extra interior space and the four extra miles per gallon, Toyota says the new Prius is quieter, safer, and more agile.

Like the current Prius, an "energy monitor" display gives you a constant guide to your gas mileage, encouraging careful driving to maximize your fuel efficiency. But the new Prius will let drivers select one of three driving "modes": EV-Drive (a mile's worth of low-speed gas-free driving powered only by the electric motor), Eco (maximizing gas mileage in normal driving), and Power (offering extra engine performance).

Another new feature is the optional solar moonroof, which has a roundabout way of contributing to fuel savings. Unlike some hand-made solar cars, the sun energy won't help power the car but will instead power an electric fan to keep the inside of the car from heating up. This reduces air conditioner usage, saving some gas.

Inside, the Prius's redesigned dashboard is more conventional than the one in the Honda Insight, though the speedometer continues to be mounted above the instrument panel rather than behind the steering wheel. As in Toyota's other new hybrid, the Lexus HS250h, many interior plastics are intended to be particularly environmentally friendly.

Toyota hasn't announced pricing yet, but the new 2010 Prius will likely cost more than the current car's base price of $22,000 when it goes on sale this spring.