By now, anyone who's shopping for a 2010 Toyota Prius knows that Toyota's newest hybrid is a smash hit.

Global demand is high, the company is making as many cars as it can get battery packs for, and the US Cash-for-Clunkers program has boosted sales of the new hybrid even above already-high demand for the redesigned 2010 model.

But the company got caught off-guard in another way, too: The solar moonroof option has been far more popular than Toyota expected, and buyers have ordered it at rates much higher than the company had imagined.

Jim Lentz, president of Toyota Motor Sales, told last week's Automotive Briefing Seminars for industry executives that Toyota had expected a "take rate" of 2 to 3 percent. The actual figure? "Demand has been running closer to 12 percent," Lentz said.

The photovoltaic solar cells in the optional roof run ventilation fans that pull hot air out of the car's interior while it's parked, reducing the load on the air conditioning when the driver returns. That cuts fuel consumption and improves gas mileage.

In some areas of the US, the 2010 Toyota Prius is now essentially sold out. The 2010 Prius, in fact, is the fourth most-popular vehicle purchased under the US government's "Cash for Clunkers" plan, and its sales have soared since that plan started in late July.

Toyota executives now say US sales will be in the range of 130,000 to 140,000 vehicles for the first 12 months, short of 2007's sales record of 180,000-plus deliveries. They blame capacity constraints and global demand.

2010 Toyota Prius

2010 Toyota Prius

[Automotive News (subscription required), WardsAuto]