It's a time of great uncertainty for leading residential solar installers. But there are positive signs with energy companies serving a different part of the residential sector: PACE.

Renew Financial, one of the largest purveyors of property-assessed clean energy (PACE) financing, has been in the business for nine years, since founder and CEO Cisco DeVries pioneered the mechanism at the Berkeley city government. PACE lets homeowners buy higher-end energy efficiency and solar improvements with no money down, by distributing the cost across property tax payments over many years. 

It's taken some time for the approach to spread. For some customers, perhaps, it's hard to get them excited about property tax assessments. And since these assessments happen locally, PACE financiers spent a lot time on policy formation at the city and state level to make this business viable.

That work culminated in a billion-dollar payoff.

"We've done a billion overall and we're going to try to do that again this year," said DeVries, referring to the dollar value of the company's financing deals. "That's what we're on pace to do. I have hundreds of millions of dollars of capacity that I'm already spending."

After all those years building up the model, it's reached a point where Renew could eclipse nine years of business in 2017 alone. Other leading PACE providers like Renovate America and Ygrene are accelerating, too. Americans spend $150 billion annually on home energy improvements, DeVries said, so there's a massive potential market for the PACE companies to chase.

"Most of this is still an education, engagement and market transformation phase, so there's a long way to go before our growth comes at the expense of somebody else," he said.

The Renew business model can scale in part because its fixed costs are low. The company spends "hardly any" money on customer acquisition, opting instead for a channel-driven approach.

In California, the largest PACE market, Renew has vetted and partnered with 2,500 contractors. They serve as the front line for customer engagement, because they're the ones getting calls when a furnace goes out or a roof starts to leak. The partnership with Renew allows the contractors to pitch higher-efficiency products that might be out of range otherwise -- the PACE model unlocks a long-term financing plan with a low cost of capital.

"It's not just providing the financing, which is critical; it is finding people at the moment when they're going to have to make an energy improvement anyway," DeVries said. "If they've already done it, they're not going to touch their furnace again for 30 years. That improvement is going to sit there and it's going to do a bad job for them, costing them money and wasting energy for 30 years."

When the timing is right and the needs of the customer match the service PACE provides, everybody gets something. The contractor can make more money and get paid quickly and in full by Renew; the customer gets a nicer home improvement that saves more money in the long term; Renew makes money; and the process facilitates a reduction in carbon emissions.

As this financing option grows in popularity, it's not hard to imagine less diligent actors chasing those dollars. Without the proper safeguards, an overly zealous PACE purchase could burden a homeowner's property taxes beyond what they can pay off, leading down a dark financial path.

So far, DeVries noted, nobody in the U.S. has gone into foreclosure due to PACE. State Sen. Nancy Skinner has introduced legislation in Sacramento to impose a minimum standard for consumer protection in PACE, a bill the company supports. It's in the industry's interest to keep that foreclosure count at zero.

The success of PACE financiers feeds directly into the success of the solar installers they work with (about 20 percent of Renew's business is solar PV installation). This particularly helps the "long tail" installers, those local companies that don't have the same kind of financial clout as their nationwide brethren.

For those major installers, there may be lessons here about how to strategically avoid paying lots of money to acquire customers, and instead leverage local partners to find buyers at the moment they're most primed for a big energy purchase.