The surge of financing money flooding into residential solar continues.

OneRoof Energy just announced that it added another $100 million to its financing with support from Morgan Stanley and Main Street Power Company and debt financing from other banking sources.  

This fund brings the total announced funds for residential solar projects in the U.S. to $3.6 billion, and $350 million already in 2013, according to Shayle Kann, Vice President at GTM Research and author of a just-published report on the U.S. residential solar PV financing industry.

OneRoof has also raised more than $80 million in operating capital and finance capital from Hanwha, Black Coral Capital, U.S. Bank (a subsidiary of U.S. Bancorp; NYSE:USB), The Quercus Trust, Yellowtree Energy, and Spring Ventures.

This is a different model than SolarCity (vertically integrated solar installation and financing) and Sunrun or Sungevity (which take an equity stake and help originate the customer).

Shayle Kann, Vice President of Research at GTM, said that in addition to the usual third-party financing companies such as SolarCity and Sunrun, the industry should keep its eye on newcomers with a unique twist on financing such as OneRoof and Vivint.

Well, OneRoof's original twist was leveraging the roofing industry. But that seems to have changed, and the company, with employee-roots in LBL Financial, looks a lot like a pure financial-services and leasing company. This is more along the Clean Power Finance model. (SolarCity talks about leasing here.)

According to OneRoof investor Rob Day of Black Coral Capital, "What we've liked about OneRoof from the beginning is the firm's ability to execute on this type of role with a wide range of different leadgen and installation partners, rather than having to take on all that downstream services work internally, which has been both a blessing and a curse for those other players. We've seen the proof of OneRoof's ability to execute in this role as we've seen their growth and seen funders migrate to them from some of those other players -- and this partnership with MorganStanley is one good example now out in the public eye."

CEO David Field said that OneRoof has financed 2,000 rooftops so far and has a goal of financing 8,000 to 10,000 rooftops in 2013. He added, "The focus is on acquiring customers [...and] driving down the cost of customer acquisition."

Field pointed out that the most recent fund structure was more of "a third-party fund" rather than the previous "proprietary fund." Field added that achieving "the lowest cost of capital is our focus."

"Financial advisors and mortgage brokers are the fastest growing sales channel -- because this is a financial product."

The firm looks to triple the amount of its financing in 2013 to $300 million.     

About 60 percent of OneRoof's projects use minority investor Hanwha's solar panels -- looking to leverage Hanwha's balance sheet for better warranties. The CEO also cited Hanwha's connection to Silent Power with the opportunity to finance solar and energy storage in places like Hawaii where the combination might make sense. 

Third-party ownership (TPO), as offered here, has become the leading finance model across the big residential markets in the U.S. According to GTM Research's recent report, Residential Solar PV Financing: The Vendor, Installer and Financier Landscape, 2013-2016, "Third-party financed residential installations comprise greater than 50 percent of new capacity in California, Arizona, Colorado and Massachusetts, with the model gaining greater market share in other states such as Connecticut, Hawaii, Delaware, Maryland, New Jersey, New York, Oregon, Texas, Vermont, and Washington."

With all that growth, there are some headwinds in the third-party-ownership world. There's the Treasury investigation into the 1603 grant program amidst questions that companies such as SolarCity, Sunrun, and Sungevity have been embellishing the prices claimed on their grant paperwork. Another potential obstacle to TPO is the plummeting cost of solar, which makes solar increasingly easier to purchase outright. Shayle Kann points out the other shadows in the distance: the net-metering debate, the expiration of the ITC, the decline of state incentives, and the availability of project finance to scale with the aggressive ambitions of all of these companies.

GTM Research sees the residential solar financing market in the U.S. growing from $1.3 billion in 2012 to $5.7 billion in 2016.