Ten years ago, Billy Parish visited the shrinking Gaumukh Glacier, a source for the Ganges River that provides 450 million people in Asia with water. Someone told him during the tour that a few years before, he would have been standing on a significantly larger glacier, but by 2030, the entire formation would be gone.

After the trip, Parish was about to start his junior year at Yale. Instead, he dropped out and founded the Energy Action Coalition. By the age of 21, he was running the largest youth organization working on clean energy solutions in the world. Rolling Stone named him a "Climate Hero."

A few years ago, Parish and his now-co-founder Dan Rosen envisioned a "Kickstarter for solar" when they realized it is estimated to cost trillions of dollars to power the infrastructure of the world with 100 percent renewable energy.

"We soon recognized that the transition from fossil fuels to clean energy represented perhaps the largest wealth creation opportunity of the century," Parish said. "There’s enormous demand for investments with these characteristics but no real platform to make investing in them easy."

The two men decided to change that with a startup called Mosaic, a web platform that allows investors to fund various solar power projects.

"For me, Mosaic represents one of the biggest business opportunities and one of the biggest climate solutions on the planet," Parish said. "To be able to work at the center of the venn diagram of those two circles is pretty incredible."

Crowdfunding: Changing the solar power equation

Less than 24 hours after Oakland-based Mosaic allowed crowdfunding campaigns in January 2013 in which investors could pitch as little as $25, they raised enough money to fund four clean energy projects in California for affordable housing projects. More than 400 investors raised $313,000. The investors, on average, paid about $670 each.

Last week, Mosaic launched a new platform on their site, allowing people to finance solar arrays on homes, in addition to the commercial projects already being funded. Since its initial launch in 2010, company has raised more than $7 million in investments through crowdfunding with a 100 percent payback rate. In its seed rounds, Mosaic raised $3.4 million from venture capitalists. In 2012, Mosaic received a $2 million grant from the Department of Energy.

The biggest project to date is installing solar panels on 1,500 military homes in Fort Dix, New Jersey. Another successful project included installing a solar roof on Pinnacle Charter School in Denver, Colorado, which doubled as clean energy education for the students.

Image: Mosaic

Mosaic charges a 1 percent fee on each investment and a small percentage fee on each origination loan. Investors can earn a 4.5 to 7 percent return on rooftop power plants. The loans are typically paid back over 10 years. Investors pay a minimum of $25 to fund one of these projects, so most of the investments are small to medium scale. According to Mosaic, most of the projects cost a couple hundred thousand dollars and have an average of a couple hundred investors.

"Our projects are successfully financed because people want to know what they are investing in and Mosaic offers solar projects as transparent investment opportunities," Parish said.

Mosaic launched a new platform last week for residential solar roof projects, which allows people to lend and invest in solar systems whether or not they are able to actually use the power themselves. For instance, if their own roof is too shady or they are renting an apartment instead of owning a home, they can still be involved by loaning money to a solar project and earning a return on their investment.

Laws to regulate these are created on a state-by-state basis through virtual net metering, which is a tariff arrangement that enables a multi-meter property to allocate solar system credits to other tenants. Currently, only 11 states allow this: