The feature might be offered in the United States, too.

The plug-in hybrid version of the new Toyota Prius will be offered with a solar panel integrated into the roof in select global markets, including Japan and Europe.

The panel takes up nearly the entire length of the roof panel. The electricity that it generates is sent directly to the battery pack when the car is parked, and it is used to power accessories such as the A/C and the lights when the car is running. All told, Toyota claims that adding a battery pack makes the plug-in Prius up to 10 percent more efficient.

The solar panel won't be available when the Prius Prime lands on our shores. However, we might see the technology in the United States a little later into the car's production run, according to industry trade journal Automotive News.

"We would like to introduce this, at least in the lifetime of the current model. It should be possible to do a lot of charging this way in places like California or Arizona," explained Koji Toyoshima, the chief engineer of the Prius, in an interview with Automotive News.

Selling a Prius equipped with a solar panel in the US is easier said than done. In Japan, the solar panels are installed on a type of reinforced glass sheeting that doesn't comply with the rollover standards here. The company is working hard to develop a system that's compliant with crash test regulations, though it's too early to tell when we'll see it and how much it will cost.