Installing a rooftop solar kit can be pricy. But the cost of affixing panels to your rooftop may not be the only factor keeping low-income communities from transitioning to the distributed, clean power source. A new study shows that even if solar installation was free, there would be another problem: The grid is limited by how much rooftop solar it can handle, and wealthy, white communities have more capacity than low-income Black and Asian ones.
The new findings, published in Nature Energy this week, suggest that the limitations of the grid itself are reinforcing economic inequalities in California, which is the state that produces the most solar energy. “Households in increasingly Black-identifying and disadvantaged census block groups have disproportionately less access to new solar photovoltaic capacity based on circuit hosting capacity,” the study found.
“A few recent studies have pointed to inequitable purchase of rooftop solar PV,” Duncan Callaway, an associate professor in Berkeley College’s Energy and Resources Group who co-authored the paper, wrote in an email. “We wanted to understand whether any goals policymakers might set to alleviate this inequity would be limited by the grid’s capacity to host new rooftop PV systems.”
Installing household solar systems leads to an uptick in energy flow onto the grid. If everyone installed panels, the grid would overheat and collapse due to the additional electric current flow.
The authors focused on the two largest utilities in California that cover the two regions which use the most solar energy in California: PG&E, which covers 5.5 million people in Northern California, and Southern California Edison, which provides power for 20 million residents in the southern part of the state. The authors pored over the utilities’ own maps that show how much voltage the electric grid can handle neighborhood to neighborhood and then compared those maps to census data on racial and class demographics at the block level.
The findings suggest that the two utilities’ grids only have the capacity to support enough solar power to meet all the electricity needs of less than half of the households they serve. Thirty-nine percent of households served by PG&E can’t even access enough grid capacity to charge an electric car or run space and water heaters, which the authors say are “the least power-intensive new loads.” It’s even worse in SCE’s operating area: There, 74% of homes can’t access that minimum level of capacity.
What’s more, the study found that those constraints “reinforce demographic disparities.” In other words, communities of color and poor communities have disproportionately less grid capacity to host household solar.
Overall, more capacity is available in majority non-Hispanic white and Hispanic communities than is available in majority Asian and especially majority Black regions.
“The total circuit capacity for generation decreases with increasing percentages of Black-identifying residents, and is disproportionately lower for census block groups with Black-identifying populations than for other racial and ethnic groups,” the study said.
There were also disparities between rich and poor census tracts, with wealthier people having more access to energy capacity.
The reason for all this, the study says, is mainly that the electricity grid is outdated. Systems were created to send electricity from a power plant to homes, but with the rise of solar power, homeowners have started producing electricity and sending it onto the grid instead. This leads to increases in current flow, which can lead to high temperatures and voltages that the grid can’t support. Utility providers have made upgrades to their infrastructure to allow the grid to support more flow, but they haven’t upgraded all areas equally.
The study comes shortly after the Biden administration announced big plans to increase the country’s solar generation. The White House found that data suggests solar panels are now so affordable that they will be able to produce 40% of the country’s electricity by 2035, or enough to power all American homes. It says part of the plan to increase solar will be to reward utilities for adding more of it to the grid, including rooftop solar.
But the lack of grid upgrades in poor communities could pose major constraints, creating neighborhoods with options for producing clean energy and others that won’t have the same choice. It seems California, and likely the nation, will need to invest in major upgrades to distribution infrastructure if rooftop solar is going to play a big role in the energy transition.
“Our primary recommendation is that policymakers and regulators continue to think carefully about the grid upgrade costs to achieve high, equitable adoption of rooftop solar PV,” said Callaway. “If they don’t, we may eventually wind up deciding, as a society, that the costs of rooftop solar are too high. If that day comes, and we still have inequitable access to solar, we will have missed an opportunity to address some of the structural inequities that are present in our energy system.”