Solar service providers are becoming a powerhouse in the U.S. residential solar market.

In 2012, leases and power purchase agreements accounted for half of all new residential installations in major markets. In Arizona, 90 percent of installations on homes were third-party-owned and -financed last year.

These financial products have opened up a whole new range of customers that couldn’t previously afford solar, bringing record amounts of solar on-line in the process. They’re also raising questions about whether solar services will be the dominant model going forward.

Providers of these services believe so. To companies like Clean Power Finance, SolarCity, Sunrun, and Sungevity, homeowners care more about the ease of interaction in a one-stop-shopping environment. As with satellite television, for example, the consumer pays for the service -- they don’t care about owning the actual hardware.

But there’s also another model to consider when talking about the difference between solar leasing and solar ownership: automobiles. Around 80 percent of consumers choose to own their car rather than lease. Cars are a symbol of independence in America, and owning is often the preferred option.

So will solar go the way of satellite television or the automobile?

“I see no reason why it can’t be more like the auto market,” says Sara Ross, co-founder and CEO of the solar services startup Sungage.

Sungage has just partnered with Connecticut’s green energy bank to roll out a new fifteen-year, 6.49 percent fixed-interest loan in the state. The company partners with installers approved by the green bank and gives them access to an online "solar wealth calculator" that displays system specifications and loan terms in an easily digestible format.

Here's what an installer would send to a customer before arranging the loan:

Ross doesn't think of Sungage as a solar utility like a solar services firm might be classified. Rather, it sees itself like an auto finance company making the process of purchasing at the dealership simpler.

"Think of us like the Toyota Finance of solar," she says.

The $1.5 million pilot launched in Connecticut this week will support about 70 solar installations. Assuming the program goes well, Sungage wants to attract pools of consumer debt and project finance to scale up the program in other states and try to compete with solar service providers.

"Leasing was the first business model out of the gate. Some of that had to do with the residential investment tax credit being capped. But that has changed and there will always be consumers who want to own their system. We want to meet that demand," says Ross.

Sungage isn't the only company that sees potential in solar ownership. Also this week, the Arizona company Sun Valley Solar Solutions released a 12-year loan in partnership with the Bosch Group for residents in that state.

Of course, debt is commonly used to finance residential solar systems through local or regional banks. And property-assessed clean energy programs, which allow homeowners to finance their systems through property taxes or other municipal taxes, have also opened up new doors for solar. But there's a lack of debt-based products that are as easy as solar leases or power purchase agreements, says Ross.

"SolarCity has gotten Google to be an investor on your roof; Solar Mosaic has allowed you to be an investor in someone else's project; but there still aren't a lot of innovations on how to get you to invest in your own project."

Which financial products dominate will depend on how customers view solar as it becomes more of mainstream. Will purchasing solar simply be about ease of interaction? Or will ownership become a central driver as solar gets more affordable? For now, it seems simplicity is winning the day. But that's certainly not a foregone conclusion -- it certainly wasn't in the auto market.

Tags: automobiles, banks, finance, power purchase agreement, solar leasing, solar loan, solar services