A recent study co-authored by Minghao Qiu, assistant professor at Stony Brook University, has found that the climate benefits of solar power in the United States vary significantly by region. The research, published in Science Advances, indicates that increasing solar power generation nationally by 15 percent could reduce annual carbon dioxide emissions by 8.54 million metric tons.
Qiu, who holds joint appointments in the School of Marine and Atmospheric Sciences and the Program in Public Health at Stony Brook, explained the importance of understanding how solar generation affects emissions on a detailed level. “We wanted to go beyond the national average and understand the finer details of how solar generation affects carbon emissions hour by hour, region by region,” said Qiu. “It’s about producing clean electricity, but also about knowing when and where that electricity replaces the dirtiest generation sources.”
The study was led by Rutgers University with collaboration from Harvard T.H. Chan School of Public Health. Researchers analyzed five years of hourly data from the U.S. Energy Information Administration and divided the country into 13 regions to model how increased solar output would affect emissions locally and in neighboring areas.
Findings showed substantial contrasts between regions. California, Florida, parts of the mid-Atlantic, Midwest, Texas, and Southwest saw notable emission reductions with small increases in solar power. Other areas like New England, Tennessee, and central states experienced smaller impacts from similar increases.
“If you have limited resources to invest in solar, you want to place those resources where they displace the most fossil-fuel-based electricity,” Qiu said. “That’s where you get the biggest bang for your buck, both for emissions reductions and for public health benefits from improved air quality.”
The research also highlighted spillover effects due to the interconnected U.S. power grid; clean energy produced in one region can reduce fossil fuel use elsewhere. For example, a 15 percent increase in California’s solar capacity was linked with daily CO₂ reductions exceeding 900 metric tons in the northwest and nearly 2,000 metric tons in the southwest.
“This interconnectedness means that clean energy investments can have benefits far beyond the state or region where they’re installed,” Qiu explained. “It shows the value of coordinated efforts between regions and across state lines.”
The team developed a statistical model capturing both immediate emission reductions when solar replaces fossil fuels as well as delayed effects caused by shifts in which power plants operate throughout a day.
“Electricity systems are dynamic,” Qiu said. “When you add solar in the middle of the day, it doesn’t just reduce emissions right away, it can also affect which power plants are running in the evening, which changes the emissions profile later on. Our model was able to capture those subtler, downstream effects.”
These downstream effects have implications for public health because fossil fuel combustion is a major source of fine particulate matter associated with serious health risks such as asthma and heart disease.
Qiu believes these findings can inform energy policy at federal and state levels as well as private sector decisions: “Utilities, grid operators, and investors all have a stake in making solar deployment as effective as possible,” he said. “This kind of analysis provides a roadmap for where investments will have the highest returns in terms of CO₂ reduction.”
He emphasized that strategic deployment is key: “We’re going to need a lot more clean energy to meet our climate targets, but we also need to be strategic,” he said. “The same amount of solar power can have dramatically different impacts depending on where and when it’s generated.”
For companies investing through renewable energy purchase agreements with sustainability goals, Qiu added: “If those companies want their investments to have the maximum climate benefit, our data can help guide them to the right regions.”
Transmission infrastructure is another factor influencing outcomes; excess clean electricity during peak sunlight hours may be wasted if transmission capacity is insufficient—a problem known as curtailment—highlighting opportunities for expanding grid infrastructure.
Pairing solar with battery storage could further enhance its impact by allowing renewable energy produced during daylight hours to offset fossil fuel use during periods of high demand later in the day.
“These findings are directly applicable to decisions being made right now about where to put solar farms, how to design energy storage systems, and how to coordinate clean energy policies across regions,” Qiu explained.
He sees this modeling approach extending beyond solar: it could apply to wind energy or emerging technologies like green hydrogen—and help evaluate combined impacts from multiple sources.
“As the energy transition accelerates, we need tools that can help us navigate complexity,” he said. “Our work demonstrates how big data and computational modeling can provide the clarity needed to make informed, impactful choices.”
“This study is about making sure we get the most out of every solar panel we build,” Qiu said. “If we can target our investments to the places where they make the biggest difference, we can accelerate the transition to a cleaner, healthier, more sustainable energy future.”