When Toyota introduced the Prius, it quickly became one of the most highly preferred hybrids available. However, as more and more companies developed their own hybrid vehicles, the popularity of the Prius began to slip. In an attempt the regain their dominance in the alternative energy realm, Toyota has secretly been developing a solar powered vehicle they hope will see mass production.
The news of this development originated from a Japanese Business paper called the Nikkei. According to their sources, the system will use solar panels mounted on the vehicles, as well as a solar array mounted on the owner's home. Between the two charging systems, the vehicle should be able to take care of a daily commute without an issue.
The Prius is the most likely candidate for the addition of solar power, seeing as there are already a handful of companies that will engineer a solar array onto your Prius for extended range. There is also an aftermarket kit you can purchase that will charge the second-generation Prius enough to run a 20 mile commute.
As far as time in concerned, those same sources also let out that it will be years before any such plans are put into full swing if it does make it into production.