Silicon Valley-based SunPower Corporation is looking to add a bit more juice to your rooftop, announcing its highest power and most efficient solar panel to date. The SPR-315 solar panel is based on the company's brand spankin' new Gen 2 solar cells, which have a rated power output of 315 watts and boast 22 percent photovoltaic (PV) efficiency -- that's opposed to the 7% to 17% common in most commercial PV systems. According to SunPower, that means you should get roughly 50 percent more power per square foot of roof area than the average solar panel, using half as many panels. Whether it'll also cost you half as much or not has yet to be seen, but we should find out by the time the SPR-315 solar panels are available in the Spring of next year, after we too have coated our country cottage in the stuff, and start contributing to -- not pulling from -- the grid.