Its goal is to offer homeowners peace of mind and open the door to securitization

SAN FRANCISCO — Privately held solar financing company Mosaic and Enphase Energy Inc. have formed a partnership to offer residential solar-power loan packages that include system maintenance as part of the deal, the companies said Tuesday.

The program provides homeowners who might purchase the solar panels peace of mind by providing upkeep services. It is also a "significant step forward" toward securitizing residential solar loans, Oakland, Calif.-based Mosaic said. That would allow large investors to bundle and sell solar-power loans like they do with mortgages.

Lenders and investors have considered residential solar loans as riskier than residential solar leases because of the issue of who will maintain the panels. Solar-panel leases typically include maintenance service by the leasing company. Offering a guarantee of service by Petaluma, Calif.-based Enphase ENPH +0.02% will make the loans more appealing to conservative investors, Mosaic said.

In the typical solar-lease agreement, homeowners are usually locked in to a decades-long contract but pay little or no money up front for a system on their roofs. Lease payments are usually smaller than monthly electricity bills, but homeowners often miss out on state and federal incentives by not buying a system outright.

Solar-panel leases were popularized by privately held SunRun Inc. and SolarCity Corp. SCTY -0.40% .

Mosaic in March launched a loan product in partnership with solar developer and installer Real Goods Solar Inc. RGSE -1.96%

SunPower Corp. SPWR -3.82% last month said it closed on a $200 million loan program to fund residential solar projects over the next two years. Homeowners interested in going solar would apply for a loan of up to $60,000 to cover installation costs.

Meanwhile, shares of solar-power companies and renewable energy companies fell on Tuesday, tracking the broader U.S. equity market following records last week. Earnings season unofficially begins after the market closes Tuesday, with Alcoa Inc. reporting its second-quarter results.

Among the hardest hit solar shares, U.S.-listed Jinko Solar Holding Co. JKS +0.15% declined 6.5%. Shares of SolarCity retreated 5.2%, and SunPower was off 5.5%.