There’s a new trend in solar—at least in California: More middle-class homeowners are installing solar than ever before. As such a new crop of cities are showing tremendous growth in solar. That’s according to a new report by SunRun and PV Solar Report that looked at full-year 2011 residential solar growth across the state.

The report found that San Jose, Bakersfield and Simi Valley were the cities with the greatest growth of residential solar. But it also found that other cities, like Hemet and Apple Valley, are also showing a lot growth in the market segment.

The cities in the top-10 list have large populations of homeowners with median incomes. SunRun spokesperson Susan Wise said it wasn’t much of surprise that such areas are taking to solar quickly. The company has seen similar geographic patterns in sales for 2011.

One of the main drivers for the increase is the availability of third-party ownership systems, wherein the homeowners pay little to no upfront costs for a solar system, like SunRun’s solar power service option.

The report found that the majority of homeowners in California put solar on their homes through such arrangements.

“In December it was about 73 percent. If you look at the year on the whole it was closer to 55 percent or 60 percent,” Wise said. “In 2012 at the end of the year it will be about 75 percent of the market, and other states will follow suit on that trend.”

Still, residential solar has a way to go.

“Solar penetration is still very low in the grand scheme of things,” Wise said. “Education is improving; people are more likely to go solar as their neighbors do. A lot of people are switching because cost [of solar] is going down.”

SunRun is working to help foster and grow that awareness in a wider range of communities.

The report helps SunRun understand solar markets in California.

“We have a broad range of things that we look at to uncover areas that have high growth potential,” Wise said. “But it does help to look within those cities, where there’s been a lot of growth in solar. But from that same data you may see where adoption is lower and that’s an indication of where we may need to engage in more markets.”

As more people become aware of the options for no-upfront-cost solar systems, SunRun expects more people in lower income brackets to make the switch.