While Toyota's press conference today at the Los Angeles Auto Show covered the new 2011 Toyota Sienna minivan, a very special Prius hybrid on the show floor signaled the company's first tentative step into the world of plug-in vehicles.

Toyota will deliver the first of 150 Toyota Prius Plug-In Hybrids early next year. But they will go only to "select partners" who will add the cars to their fleets.

The company says the Prius Plug-In Hybrids are for "market/consumer analysis and technical demonstration." Its goal is to accumulate real-world data on how and where users plug in their cars, how often the cars run in full electric mode or revert to "hybrid mode," like a regular Prius.

2010 Toyota Prius Plug-In Hybrid, 2009 Los Angeles Auto Show

2010 Toyota Prius Plug-In Hybrid, 2009 Los Angeles Auto Show

2010 Toyota Prius Plug-In Hybrid, 2009 Los Angeles Auto Show

2010 Toyota Prius Plug-In Hybrid, 2009 Los Angeles Auto Show

That's still a long way from dealership sales to consumers, but it signals Toyota's extreme caution on progressing beyond its known Hybrid Synergy Drive system. The company officially unveiled the Prius Plug-In Hybrid at September's Frankfurt Motor Show, but this was its first U.S. showing.

Toyota has built about two-thirds of all the hybrids in the world, including 1.5 million Priuses, but none of them plug in to recharge the battery from the electric grid,

Ten of the 2010 Toyota Prius Plug-In Hybrids will go to a research project in Boulder, Colorado, jointly run by the University of Colorado and the U.S. Department of Energy. They will be driven by Boulder residents whose drive cycles and power usage will be tracked for two years.

Toyota claims the Prius Plug-In will run up to 13 miles on electricity only, and can achieve speeds up to 60 miles per hour on electric power.

The ability to run electrically for short trips, and in hybrid mode thereafter, "alleviates the issue of limited cruising range" found in battery electric vehicles without gasoline engines, Toyota says.

Unlike the standard 2010 Toyota Prius, with its nickel-metal-hydride battery pack, the Prius Plug-In Hybrid uses a lithium-ion pack with more energy capacity: roughly 4 kilowatt-hours as compared to the standard pack's 1.6 kWh.

This month, Toyota will deliver the first of 350 Prius Plug-In Hybrids in Europe and Japan. They, too, will go to business and government partners, not actual consumer car buyers.

Toyota has only committed to building 500 Prius Plug-In Hybrids. Meanwhile, Prius owners and even some electric utilities are on track to exceed that number of plug-in hybrids using third-party conversion kits.