At 50 miles per gallon, the 2011 Toyota Prius five-door hatchback is the most fuel-efficient car sold in the U.S.

But, says Toyota, its customers told the company they needed more room--for people, for stuff, for stretching out.

So the quintessential Prius hybrid is becoming not just a vehicle but a family. Its first new member is the Prius V, which you can view as somewhere between a station wagon, a tall hatchback, and a minivan-without-sliding doors.

2012 Toyota Prius V

2012 Toyota Prius V

Whatever you call it (Toyota just says the "V" means "versatility"), while the Prius V sits on the same platform as the hatchback and is recognizably a Prius, most of the sheetmetal is different. It's taller, longer, and squarer at the rear.

It uses the same 1.8-liter engine and Hybrid Synergy Drive system, and in comparison to the hatchback's EPA ratings of 51 mpg city, 48 mpg highway (50 mpg combined), the Prius V is rated at 42 mpg city, 38 mpg highway, for a combined rating of 40 mpg.

To put that in perspective against the hatchback's 50 mpg, the Prius V--with 50 percent more interior space--uses roughly 2 quarts more fuel every 100 miles.

Other features of the Prius V include a sliding second row of seats that include a 45-degree recline, 60/40 split seat back, and 34 cubic feet of cargo space behind the rear seats.

Toyota is offering for the first time on any car a Panoramic Moonroof with retractable power sunshades. Compared to a glass roof of the same size, its resin material weighs 40 percent less--contributing to fuel efficiency--as well as insulating against sun heat.

2012 Toyota Prius V

2012 Toyota Prius V

A backup camera, pushbutton start with smart key, Hill Start Assist Control, and four driving modes--Normal, Power, ECO, and EV--come standard on the Prius V.

Options include LED headlamps, adaptive cruise control, and an advanced self-parking system.

The Prius V will be the first car fitted with Entune, Toyota's multimedia and mobile communications system. It supports mobile apps, including conveniences like OpenTable and, plus travel services like live weather, traffic, and fuel information.

2012 Toyota Prius V

2012 Toyota Prius V

Music options include Pandora's personalized music, iheartradio with more than 750 stations, and the increasingly standard ability to control personal music players via USB or Bluetooth streaming.

The Entune system also reads back and replays text messages, allows drivers to respond with canned replies, and operates various functions via voice recognition to reduce driver distraction.