Study finds a 15% solar power boost could cut US CO₂ emissions by millions of metric tons annually

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 was published 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 include Danielle Braun and Daniel Mork.