California grid limits may worsen inequitable access to solar energy: study

California grid constraints could exacerbate the existing racial inequities tied to solar energy adoption, a new study in Nature Energy has found.

The prohibitive upfront costs associated with solar installations have already driven a wedge between those who can and cannot afford to integrate such clean technologies on their rooftops, according to the authors. But the structural limitations of the state’s electricity grids are also reinforcing these gaps, leaving Black-identifying and disadvantaged populations with “disproportionately less grid capacity to host renewable solar energy,” they observed.

The installation of household photovoltaic (PV) systems causes an increase in current flow, leading to high temperatures and voltages that constrain the grid, the authors explained. As a result, the number of households able to install such systems is limited.

“In the engineering literature, researchers have been studying the technical barriers to deploying solar,” Anna Brockway, the study’s lead author and a Ph.D. candidate in the energy and resources group at the University of California, Berkeley, told The Hill.

“We wanted to connect these two threads of inquiry — disparities related to equity around current deployment, and technical barriers from the engineering side — to see if there was something we could learn about the practicalities of adoption,” she said.

To evaluate the limits of integrating such “distributed energy resources” (DERs), Brockway and her colleagues mapped the grid capacity of California’s two largest electricity providers: Pacific Gas and Electric (PG&E) and Southern California Edison (SCE), which together serve more than 30 million people, according to the researchers.

While their study focused on rooftop solar panels, DERs are the umbrella group for all small-scale electricity supplies spread out over wide areas — also including equipment like backup batteries and emergency diesel generators, according to the Department of Energy.

After analyzing the results alongside relevant demographic data, the authors found that the PG&E and SCE grids only have enough capacity to support photovoltaic systems in less than half of their connected households — and that the capacity limits “reinforce demographic disparities” in access, said a news release accompanying the study.

In PG&E’s territory, the authors found that 39 percent of households cannot access “even the least power-intensive new loads,” such as space and water heating or “level-1” electric vehicle chargers — the slower, standard chargers that come with an EV.

“Hosting capacity for DERs decreases for households in increasingly Black-identifying and disadvantaged communities,” the authors noted, stressing that correlations between hosting capacity and race were “the starkest” among a series of other demographic indicators analyzed.

The authors also identified higher median levels of such distributed generation in non-Hispanic white and Hispanic census block groups when compared to Black or Asian populations. As far as disadvantaged communities are concerned, the authors found disparities among wealthy and poor populations, observing linguistic isolation as a possible barrier to DER adoption.

The researchers also observed “that the total circuit capacity for generation decreases with increasing percentages of Black-identifying residents” — meaning the circuits located in Black communities “cannot currently support the same PV deployment.”

As more households install solar rooftops and acquire electric vehicles, electricity grids could become even more strained and the gap for equitable DER access could widen further, the researchers warned.  

“If grid limits are not considered,” they wrote, “further inequities may emerge.”

Already, Brockway told The Hill, the California Public Utilities Commission has set a goal to “consistently integrate equity and access considerations” in the clean energy transition.

Meanwhile, costs associated with rooftop solar systems “have plummeted in the last 10 years, to the point where the lifetime cost of solar is below the cost of electricity for nearly every customer in California,” co-author Duncan Callaway, an associate professor of energy and resources at Berkeley, told The Hill.

“The challenge is finding pathways to identify and equitably finance a diverse array of customers,” he said.

As policymakers try to help specific communities adopt solar energy, Callaway said they will need to consider just how expensive grid upgrades will be and the “significant costs” they will add to increasing access.

“It may be that alternative approaches like community solar could provide the same economic and environmental benefits to a diverse range of customers, without requiring the same grid upgrades,” he added.