A new study from the Harvard T.H. Chan School of Public Health, published on July 30, 2025, in Science Advances , demonstrates that a 15% increase in solar power generation in the US could reduce CO2 emissions by 8,54 million tons annually. The research shows how targeted investments in solar energy can deliver significant climate benefits, although the effects vary considerably by region.
The researchers analyzed five years of hourly data from the U.S. Energy Information Administration (starting in July 2018) on electricity generation, consumption, and emissions in 13 regions, including California, Texas, the Midwest, and New England. Using an advanced statistical model, they examined the immediate and delayed effects of increased solar power production. In California, a 15 percent increase in solar power resulted in a CO2 reduction of 147,18 tons in the first hour and a further 16,08 tons after eight hours.
Solar expansion showed significant emissions reductions, particularly in regions such as California, Florida, Texas, the Mid-Atlantic region, the Midwest, and the Southwest. In contrast, the effects were small in areas such as New England, Central England, and Tennessee. For the first time, the study also quantified cross-border benefits: A 15 percent increase in solar capacity in California reduced emissions by 913 tons per day in the Northwest and by 1.942 tons per day in the Southwest.
"Our findings provide policymakers with guidance to prioritize solar investments where they will deliver the greatest climate benefits," said lead author Arpita Biswas of Rutgers University. Co-author Francesca Dominici, director of the Harvard Data Science Initiative, emphasized the role of data science in achieving carbon reduction targets.
The study underscores the need for regional cooperation, as solar expansion in one region also relieves pressure on neighboring areas. Given that only 2023% of US electricity came from solar energy in 3,9, compared to 60% from fossil fuels, expansion could not only protect the climate but also bring health benefits through reduced air pollution.
Source: Harvard TH Chan School of Public Health
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