TOKYO -- The next-generation Prius plug-in hybrid gets a little greener with a the rooftop solar panel for recharging the batteries. Sun power only amplifies the eco-car cred of one of the greenest vehicles. The cells charge the car even when it is parked and can boost fuel efficiency by as much as 10 percent by allowing longer electric-only driving times. The problem: The Japan market solar panels are laid on reinforced glass sheeting that doesn’t pass America’s more stringent rollover crash tests. Next-generation Toyota Prius has solar roof for Europe, Japan Elon and the engineers here at TMC keep telling us car rooftop solar makes no sense that solar belongs on the roofs of building but I think this will be a boon for Toyota. Even if the "up to 10%" is almost never realized in the real world. Like aerodynamic aids that don't really aid aerodynamics below felony speeds people dig them.