OAKLAND -- Solar financing startup Mosaic says it wants to be the "Kickstarter for solar" -- enabling people to invest their own money in solar energy projects large and small.

But while Kickstarter -- the world's largest platform for funding creative projects, from independent films to new bistros and public parks -- relies on donations, Oakland-based Mosaic promises to pay investors back with an interest rate that varies project to project. The minimum amount to invest in a Mosaic-funded project is $25.

On Tuesday, Mosaic celebrated the successful financing of its sixth solar project on the roof of the Youth Employment Partnership, or YEP, Oakland's largest youth employment training agency. Oakland Mayor Jean Quan and dozens of YEP staff and solar industry representatives climbed onto the roof for the midday ribbon-cutting.

"We've chosen to bank on the sun," Steve Richmond, Mosaic's chief financial officer, told the gathering. "The sun comes out, and the solar panels create electricity. We buy it at a cheaper price than we can from the utility, and our investors make a return. We want to fund projects like this every week."

Mosaic, which has 14 employees, is a private, venture-backed startup that was founded in 2011. In May, it raised $2.5 million in a first round of venture funding led by Spring Ventures of San Francisco. In June, the Department of Energy awarded Mosaic a $2 million grant through its SunShot initiative.

Mosaic's other funded projects include solar on the roofs of the People's Grocery in West Oakland and the Asian Resource Center in the city's Chinatown.

Individual investors, 51 in all, joined forces to raise $40,325 needed to help buy and install the solar panels at YEP. Other costs for the installation, which is projected to save the nonprofit $160,000 in reduced electricity costs over the lifetime of the project, were covered by a grant from an anonymous donor.

Mosaic and YEP have entered a contract in which the organization leases the solar system in exchange for monthly payments based on the amount of electricity generated. Mosaic says the revenue will be used to pay back the investors with an estimated 6.38 percent annual return.

But there are risks, including that solar panels don't always produce the amount of electricity that manufacturers claim and that output can be affected by the weather. Mosaic's website acknowledges that investors could lose some or all of their investment.

Contact Dana Hull at 408-920-2706. Follow her at Twitter.com/danahull.