Why do some cities have higher low-income solar adoption rates than others?

For years, the Lawrence Berkely National Laboratory has been studying solar adoption among low- and moderate-income (LMI) households.

A new study, published in Energy Research & Social Science and led by Lawrence Berkeley National Laboratory, sought to understand why LMI adoption rates are higher in some cities than others.

It’s long been studied that households are more likely to adopt PV when they have seen PV installed on nearby rooftops or interacted with PV adopters, which has disproportionately occurred in affluent neighborhoods since high-income customers are typically the first to adopt new technologies.

However, LMI households are more likely to adopt solar when they see solar installations installed on other LMI households or interact with other LMI solar adopters than with high-income adopters.

The research, which combined statistical analysis with in-depth interviews across three cities that had relatively high LMI solar adoption rates, found that traditional quantitative approaches explain less than one-third of the variation in LMI adoption trends through socioeconomic factors.

This suggests that the full story of solar equity requires looking beyond numbers alone.

Because of this, the researchers hypothesized that cities where significant early investments were made to support solar access among LMI households would have higher LMI adoption rates today, all else equal, compared to cities where LMI solar initiatives were launched more recently.

The most frequent drivers for LMI adoption were incentives, city context, partnerships and trust building.

Incentives: Incentive programs, program flexibility, rate structure, net metering
City context: Policies and legislation, consumer protections, funding, history, urban layout
Partnerships: Community engagement, public authority, multilevel stakeholders
Trust building: Community involvement, transparency, education, outreach and marking, vetted processes

The study found that LMI adoption ratios are lower in cities with more income inequality and income segregation.

In 2023, about 68 % of all U.S. households were LMI households, while only about 49 % of PV adopters were LMI households, according to a separate study from Lawrence Berkeley National Laboratory.

LMI adoption ratios declined by about 40% when moving from the most income-equal cities to the most income-unequal cities. Additionally, the study found LMI adoption ratios were significantly lower in cities with relatively high home values.

This could be because LMI households are less likely to own homes in cities with higher property values and are thus less likely to adopt rooftop solar, the authors hypothesized. Or, it could be because LMI households allocate more LMI adoption ratios are significantly lower in cities with relatively high home values solar.

LMI adoption ratios were also lower in cities with higher owner-occupancy rates, which the researchers said countered their expectations that higher LMI owner-occupancy rates should support more LMI adoption.

All of the interviewees in each case study broadly stated that state incentive programs were critical for reducing solar adoption costs to be low enough to enable LMI adoption. Every Chicago interviewee said the state’s incentive programs, Illinois Shines and Illinois Solar for All, are important drivers of LMI adoption in Chicago.

Solar incentive program summaries
Case	Program	Summary
Chicago	Illinois Solar for All (2016 – current)	Same incentive as Illinois Shines, except that for income-qualifying customers the state requires that systems be sold to customers with no up-front costs and that ongoing payments cannot exceed 50 % of the value of the output of the systems.
Chicago	Illinois Shines (2016–current)	Provides incentives to all residential systems (subject to program capacity limits) by subsidizing the prices of renewable energy certificates generated by rooftop PV programs. According to Illinois Shines program materials, the program is predicated on the idea that installers “pass through” the subsidies to customers in the form of more competitive pricing, a mechanism that has been observed in other PV incentive contexts. Installers must comply with consumer protection requirements to receive the incentives.
Hartford	Solar for All (2015 – 2021)	The Connecticut Green Bank provides below-market rate loans to support subsidized PV leases for LMI customers. The Green Bank partnered exclusively with a single provider (Posigen) to implement the program. The program ran from 2015 to 2021.
Hartford	Residential Renewable Energy Solutions (2022 – current)	Utilities are required compensate all PV output at a specified rate. Customers earning less than 60 % of the state’s median income and customers living in “distressed municipalities” are eligible for enhanced compensation rates. As of January 2024 Hartford was one of 37 municipalities eligibility for the distressed municipality incentive.
Richmond	Single-family Affordable Solar Homes (2006 – 2021)	Program required that 10 % of California’s PV incentives be reserved for low-income households. Eligible households could receive highly subsidized PV systems. The program was implemented through a single partner-installer GRID Alternatives.

Even though Illinois Solar for All is specifically targeted for LMI customers, every Chicago interviewee but one said Illinois Shines was the more important of the two programs in driving LMI adoption in Chicago.

As of Jan. 8, 2025, Illinois Shines had supported about 94,000 small-scale solar installations, while Illinois Solar For All had supported around 1,400.

Locations of rooftop solar installations in Chicago with tract-level median incomes.
*Image: Lawrence Berkeley National Laboratory*

The interviewees gave two reasons why the non-LMI program has driven more LMI adoptions:

Illinois Shines offers lower renewable energy credit (REC) prices.
The Illinois Shines program has consumer protection measures.

A common theme across the interviews framed consumer protection measures as necessary for building LMI trust in the solar adoption process.

The interviewees from Chicago portrayed a broad culture of consumer protection across public authorities and organized community groups in Chicago, the study said.

For example, one Illinois state program provides resources for “stranded” customers who begin the adoption process with an installer who subsequently cannot or will not install the system.

In Chicago, two interviewees described the local utility, ComEd, as a collaborative partner in LMI initiatives.

According to the study, another interviewee said Chicago’s relatively well-maintained and updated grid has mitigated hosting capacity limits as a barrier to LMI adoption. They also said ComEd’s willingness to support solar initiatives contributed to collaboration. (Illinois utilities are not allowed to own generation, so unlike some other states, they do not lose sales when their ratepayers go solar.)

The case studies show how city contexts can affect LMI adoption, such as the role of supportive city governments.

(Read: For rooftop, community solar, ‘we’re all for it,’ ComEd says)

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