Sep 16, 2021 7:00 AM

An Outdated Grid Has Created a Solar Power Economic Divide

Utilities have upgraded the infrastructure for rooftop power in richer neighborhoods, but low-income areas don't have the same capacity.

If the United States is ever to make a dent in its production of planet-warming carbon emissions, it will have to crank up the use of solar energy, much of which can be generated from rooftops on homes and businesses. Solar provides only 3 percent of the US energy supply today, but the White House and states like California are pushing to boost that to more than 40 percent in the coming decades.

To get there, home and business owners will need more financial incentives to install photovoltaic panels, while large-scale solar farms also will need land and transmission lines to send power from rural areas to cities. Last week, state regulators in California required builders to install solar panels and battery storage in new commercial and high-rise residential buildings. But a new study finds some low-income and minority neighborhoods might be left behind, mainly because utilities haven’t upgraded the electrical grid equally everywhere.

Even if rooftop solar panels were free to everyone, the authors say, homeowners in these areas wouldn’t be able to use power from solar panels to run appliances or charge an electric vehicle without buying a special battery. That’s because the power grid in those areas can’t accept the additional electric current generated by solar panels.

“There isn't enough capacity for everyone to have solar power, even if that solar were free,” says Anna Brockway, lead author on the study published this week in the journal Nature Energy and a graduate student in the Energy and Resources Group at UC Berkeley. “We find those limitations are starker in Black-identified and disadvantaged communities. Those communities have even less grid capacity per household to be able to accommodate solar that people might want to obtain.”

Brockway and her colleagues studied Pacific Gas and Electric and Southern California Edison, two utilities in California, the state that generates the most solar power in the country. PG&E’s service area stretches from Mount Shasta south to Santa Barbara, while SCE’s service territory covers Los Angeles County, Orange County, and San Bernardino County, as well as the border region with Nevada. They chose these two utility districts because they have the highest use of solar power in the state. Both serve high- and low-income areas, as determined by census tract data, and together provide power to 30 million people.

The researchers compared the utility’s own maps of “hosting capacity,” which is how much power the electric grid can handle in each neighborhood, to census data on racial demographics and economics at the block level. They then estimated how much circuit capacity would be needed to accommodate rooftop solar and distribute it in neighborhoods.

For decades, the power grid has been built to send electricity in one direction—from a power plant, through transmission lines, to the home or business. But homeowners have started producing electricity and sending it the other way. In wealthier areas and whiter communities, where solar panels have become common in the past few decades, utilities have upgraded equipment so that the two-way current flow is easier. “Early adopters disproportionately fit into certain demographic characteristics of being white and of being higher income than the average ratepayer,” Brockway says.

But that’s not the case in minority neighborhoods, where rooftop solar isn’t as common. Take, for example, the transformers that connect power lines to each home or business. Older ones are not built to carry extra power generated from rooftop panels in the opposite direction. Any extra current flow would be turned into heat, which can damage or destroy the transformers. “Anytime you are moving electricity from one place to another, whether solar power or through the grid to charge something, there’s going to be an increased amount of power current flowing through the lines,” Brockway says. Those lines, she continues, “are only able to handle a certain amount of current.”

This congestion might also make it tougher to charge electric vehicles at home, says Mohit Chhabra, senior scientist at the Natural Resources Defense Council, and that will make it harder for the US to switch from gas-powered to cleaner EVs. “The fact that the grid isn't ready to take on the level of electrification that we want to isn't a good thing,” Chhabra says. “We don't want a situation where Black and lower-income neighborhoods are unable to charge their vehicle at home or near their home.”

Another problem is that substations that distribute energy often aren’t able to manage the two-way flow of electricity, and need to be upgraded.

Upgrades to an electric grid take years to complete and must be approved by each state’s public utilities commission. The cost is usually spread out among all ratepayers. Utilities need to make these upgrades more evenly across their service area if they are to accomplish goals of boosting renewable power, according to Duncan Callaway, a coauthor on the paper and associate professor in Berkeley’s Energy and Resources Group. “There will need to be significantly more upgrades to the infrastructure in areas that are low income or Black-identifying if we want to reach equitable goals for distributed solar,” Callaway says.

Callaway says that each neighborhood would require different kinds of electric grid infrastructure: “It's not like there's just one piece of equipment that you need to solve the problem.”

Because the power grid in poorer neighborhoods lacks electrical hosting capacity, according to the study, more than half of the homes served by PG&E and SCE are unable to generate enough solar power to offset all of the homes’ average annual electricity consumption. In PG&E’s territory, the study found, 39 percent of households in the entire service area lack the grid capacity to run space or water heaters, or charge an electric vehicle. In SCE’s territory, that figure is 74 percent of households.

The study did not break down hosting capacity by city or neighborhood, but rather by census tracts throughout both utilities’ service areas. So while it does not list specific regions with limited capacity, nor directly compare neighborhoods to one another, the authors wrote that they had identified an overall pattern: “With respect to race and ethnicity, we found that 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.”

Callaway and Brockway drew the correlation between hosting capacity and neighborhood demographics using maps produced by the utilities themselves. But Erik Takayesu, vice president for asset strategy and planning at SCE, says that those maps were designed to help developers of large-scale commercial solar farms locate areas where they could feed energy to the grid faster and more easily. “It was not intended to signal to the retail customer who really just wants to put that solar rooftop on or get the electric car to say, ‘No, you can't do that,’” Takayesu says. “That was not really the intent of those maps.”

Takayesu says SCE is upgrading older areas of the electric grid over time to modernize equipment to handle increased current from rooftop and provide additional hosting capacity. He says that government policies to encourage solar energy and make it more affordable are needed as well. “We won't arbitrarily upgrade [electrical] grids for demand that isn't being projected, but the policies that promote these technologies need to have the reach to disadvantaged communities so that they could be able to adopt these technologies,” he says. “And as a result, yes, we have to make sure that the grid is prepared for that.”

PG&E officials emailed a statement to WIRED saying that they are still reviewing the study: “While we are currently reviewing the report, PG&E continuously forecasts electric load in its service area, implements upgrades to the distribution grid to meet the demand and are committed to supporting the energy needs of all our customers including those in disadvantaged communities.”

Experts say it could cost up to $4.5 trillion, or about $35,000 per household, in the next 20 years to fully upgrade or “decarbonize” the existing US electric grid, according to a 2019 report by the energy consulting firm Wood MacKenzie. And a 2019 analysis by SCE says California alone will need to spend $33 billion a year until 2045 in order to reach its carbon-neutral climate goal, boost solar and other renewable forms of energy, harden the grid against wildfires and other effects of climate change, and modernize the grid to handle increased capacity.

Callaway says that the lack of hosting capacity will squeeze the growth of rooftop solar power in California, and the expense of upgrading the grid might make it difficult to reach the state’s clean energy goals. “There may be some sort of a breaking point in the future where, as a society, we decide we're spending too much on upgrading distribution infrastructure,” Callaway says. “That could lead to a policy where you start denying people the ability to get a permit to put solar PV on the roof because of the congestion,” or the grid’s inability to receive power from homeowners.

The new Berkeley study comes a few days after officials at the US Department of Energy unveiled the Solar Futures report, a new plan to increase solar to 40 percent of the nation’s generating capacity by 2035, and create 1.5 million new jobs without raising consumer electricity prices. Becca Jones-Albertus, director of DOE’s Solar Energy Technologies Office, says that the agency is developing new kinds of power current inverters that make two-way flow of electricity cheaper and easier, but that the upgrades aren’t happening as quickly as necessary.

“The uptake is slow,” Jones-Albertus says. “Utilities need to have more experience and trust in using these capabilities. As the trust grows, we should see greater hosting capacity everywhere.”

In addition to new technologies, the DOE report spells out alternatives to rooftop solar, such as community solar, in which neighborhoods subscribe to a solar farm located outside the residential area. That would allow renters and low-income residents, as well as homeowners whose roofs are either too shady or not in good condition, to get the clean energy benefits of solar power. (Studies have suggested using other public areas, like airports and California’s canals, to boost solar capacity.)

The DOE plan also includes financial incentives for homeowners to install batteries to store the power from solar panels that can be used later to charge an electric vehicle, or used during emergencies when grid power goes down.

Jones-Albertus says the Berkeley study points out an important problem that hasn’t been picked up on before. “It was very illuminating in showing the disparities in hosting capacity into these two utility regions, and is certainly worth understanding how pervasive that pattern is,” she says.

One expert who was not part of the study says that there are practical and environmental reasons to include minority communities in the drive to expand solar energy. “If you are excluding any community, you are limiting your market share,” says Deborah Sunter, an assistant professor of civil and environmental engineering at Tufts University. “So if you are trying to combat climate change, you are going to need all hands on deck. You need all communities to be participating.”