DOE study: This rooftop solar fix could slash CO2

Source: By David Iaconangelo, E&E News reporter • Posted: Wednesday, November 11, 2020

Many solar programs are not bringing lower-income people into the rooftop solar market, a trend that could “decelerate” the solar industry and slow emission cuts, according to a new study by researchers from the Department of Energy.

Solar is expected to become a linchpin of state decarbonization goals and could play a principal role in President-elect Joe Biden’s plan of reaching 100% carbon neutral electricity by 2035. Much of that growth is likely to come from large-scale arrays built by utilities and corporations.

In a report this morning, for instance, the International Energy Agency predicted that 2020 would turn out to be a year of “unprecedented” expansion for U.S. solar, with most growth coming through utility-scale projects. The distributed or small-scale solar market, by contrast, was expected to contract.

But as much as 42% of the nation’s rooftops that could accommodate solar panels are in low- to moderate-income housing, according to the study, which was carried out by analysts at the Lawrence Berkeley National Laboratory and published in Nature Energy. Reaching those rooftops could make a major difference for climate goals by helping maximize market potential, according to the researchers.

“If you forgo that [42%], you miss a huge chunk of the potential housing you could be deploying on,” said Eric O’Shaughnessy, a co-author of the paper and researcher at the Lawrence Berkeley lab.

Large-scale solar arrays would certainly play an important role in CO2 reduction but ideally not the only one, he said. “If you’re aiming toward a holistic climate agenda, rooftop solar is part of that,” he said.

O’Shaughnessy and four co-authors from the national lab examined how five state-level policies intended to encourage rooftop solar adoption, regardless of income level, had affected low- and moderate-income households in particular.

They found that only three of the five had made adoption more equitable, meaning the policy helped bring solar into new communities and expanded it to less wealthy households.

In all three of those cases, said O’Shaughnessy, the policies helped cut the upfront cost of solar systems.

Property-assessed clean energy financing (PACE), for instance, lets homeowners finance their panel systems through property taxes, with little or no upfront cost. Leasing the panels, along with incentives that target low- and moderate-income households, was similarly helpful.

By contrast, upfront rebates and other nontargeted incentives that are offered in many states were “ineffective” at promoting equitable adoption and could even exacerbate inequity, the team found.

That was also the case for community-run “Solarize” campaigns, in which members encourage each other to invest in rooftop systems while negotiating together with an installer for a discounted price.

Those policies may have encouraged solar deployment in general, but they did little to address the basic reality that high-income households are more likely to adopt rooftop units, said the authors.

That disparity could “decelerate rooftop PV deployment and has potential energy justice implications,” they wrote.

The study defined low- to moderate-income adopters as households that were earning less than the median income in counties where they were located, and considered single-family houses but not multifamily dwellings.

Lower-income households tend to pay a larger share of their income toward energy bills, noted O’Shaughnessy, meaning they stand to benefit the most from the proliferation of low-cost photovoltaics.

“A lot of people talk about rooftop solar as, maybe this could be part of the solution” for energy justice, he said. “Whereas now, it’s part of the problem. The motivation of this paper is, maybe there are some policies and business models that have begun to alleviate this problem.”