Increasing solar power could lead to significant cuts in CO2 emissions

Embargoed for release: Wednesday, July 30, 2:00 PM ET

Key points:

• Researchers estimated that a 15% increase in U.S. solar power generation could reduce CO2 emissions by 8.54 million metric tons annually, offering major climate benefits.
• The benefits of added solar power varied widely by region. Areas like California, Florida, Texas, Mid-Atlantic, Midwest, and Southwest exhibited major reductions in emissions from solar increases, while other areas, such as Central, New England, and Tennessee, saw minimal impact.
• Solar expansion in one region can reduce emissions in neighboring regions, highlighting the importance of regional collaboration in clean energy planning. 

Boston, MA—Increasing solar power generation in the U.S. by 15% could lead to an annual reduction of 8.54 million metric tons of carbon dioxide (CO2) emissions, according to a new study led by Harvard T.H. Chan School of Public Health. The researchers found that the climate benefits of solar power differ markedly across U.S. regions, pinpointing where clean energy investments return the greatest climate dividends. 

“This is an exciting study in that it harnesses the power of data science to offer insights to policymakers and stakeholders on how we can achieve CO2 reduction targets,” said corresponding author Francesca Dominici, director of the Harvard Data Science Initiative and Clarence James Gamble Professor of Biostatistics, Population, and Data Science.

The study will be published July 30 in Science Advances. 

In 2023, 60% of U.S. electricity generation relied on fossil fuels, while just 3.9% came from solar, according to the U.S. Energy Administration. Since fossil fuel-generated electricity is a leading source of both CO2 and harmful air pollutants such as fine particulate matter, cutting emissions by expanding solar could not only mitigate CO2 but also help reduce illness, hospitalizations, and premature deaths linked to air pollution exposure. 

For this study, the researchers examined five years of hourly electricity generation, demand, and emissions data from the Energy Information Administration, starting July 1, 2018. They focused on 13 regions: California, Carolinas, Central, Florida, Mid-Atlantic, Midwest, New England, New York, Northwest, Southeast, Southwest, Tennessee, and Texas. Using this dataset, they constructed an advanced statistical model to explore how increases in hourly solar energy generation would affect CO2 emissions within a given region and in its neighboring regions. 

The study quantified both immediate and, for the first time, delayed emissions reductions resulting from added solar generation. For example, the researchers found that in California, a 15% increase in solar power at noon was associated with a reduction of 147.18 metric tons of CO2 in the first hour and 16.08 metric tons eight hours later. 

The researchers’ methods provide a more nuanced understanding of system-level impacts from solar expansion than previous studies, pinpointing where the benefits of increased solar energy adoption could best be realized. In some areas, such as California, Florida, Mid-Atlantic, Midwest, Texas, and the Southwest, small increases in solar were estimated to deliver large CO2 reductions, while in others, such as New England, Central, and Tennessee, impacts were found to be minimal—even with much larger increases in solar generation. 

In addition, the study demonstrates the significant spillover effects solar adoption has on neighboring regions, highlighting the value of coordinated clean energy efforts. For example, a 15% increase in solar capacity in California was associated with a reduction of 913 and 1,942 metric tons of CO2 emissions per day in the Northwest and Southwest, respectively. 

“Our study offers policymakers and investors a roadmap for targeting solar investments where emissions reductions are most impactful and where solar energy infrastructure can yield the highest returns,” said lead author Arpita Biswas, assistant professor in the Department of Computer Science at Rutgers University. “From a research perspective, our findings also demonstrate the power of harnessing large-scale, high-resolution energy data to generate actionable insights.”

Other Harvard Chan authors included Danielle Braun and Daniel Mork. 

The study was supported by the National Institutes of Health (grants R01ES030616, RF1AG074372, R01MD016054, RF1AG080948, R01ES034021, U24ES035309, R01ES034373, R01ES037156, R01AG066793, R01ES035735). 

“Quantifying Effects of Solar Power Adoption on CO2 Emissions Reduction,” Arpita Biswas, Minghao Qiu, Danielle Braun, Francesca Dominici, Daniel Mork, Science Advances, July 30, 2025, doi: 10.1126/sciadv.adq5660

Visit the Harvard Chan School website for the latest news and events from our Studio.

###

Harvard T.H. Chan School of Public Health is a community of innovative scientists, practitioners, educators, and students dedicated to improving health and advancing equity so all people can thrive. We research the many factors influencing health and collaborate widely to translate those insights into policies, programs, and practices that prevent disease and promote well-being for people around the world. We also educate thousands of public health leaders a year through our degree programs, postdoctoral training, fellowships, and continuing education courses. Founded in 1913 as America’s first professional training program in public health, the School continues to have an extraordinary impact in fields ranging from infectious disease to environmental justice to health systems and beyond.