A new study led by University of Oxford and University College London has found that pollution from coal-fired power plants is significantly reducing the performance of solar energy systems worldwide, creating a hidden obstacle to the global clean energy transition.
Published in Nature Sustainability, the research analyzed more than 140,000 solar photovoltaic installations across the globe using satellite imagery, atmospheric observations and machine learning technologies. Researchers discovered that airborne pollution particles, known as aerosols, reduced global solar electricity generation by 5.8% in 2023 alone.
According to the study, the lost energy amounted to 111 terawatt-hours — roughly equivalent to the annual output of 18 medium-sized coal-fired power plants. Researchers warn that these losses are becoming a major but often overlooked factor affecting renewable energy efficiency.
The report highlights a paradox within the global energy transition: emissions from fossil fuel infrastructure are directly undermining the effectiveness of renewable energy systems expanding nearby. Between 2017 and 2023, new solar installations generated an average of 246.6 terawatt-hours annually, while pollution-related losses from existing systems reached 74 terawatt-hours per year.
China emerged as one of the most affected countries due to the simultaneous expansion of both coal power and solar infrastructure. The country generated more than 41% of the world’s solar electricity in 2023 but also recorded the highest pollution-related losses, with solar output reduced by 7.7%. Researchers estimate that nearly one-third of these losses were directly linked to emissions from coal-fired plants.
Lead researcher Rui Song explained that air pollution not only blocks sunlight but also alters cloud formation, potentially worsening the impact on solar generation beyond current estimates.
The study notes, however, that China has recently shown signs of improvement thanks to stricter emissions standards and the adoption of ultra-low-emission technologies in coal plants, despite maintaining large coal production capacity.
Researchers say the findings should serve as a warning for governments and energy planners worldwide. They argue that renewable energy forecasts may be systematically overestimated if pollution-related solar losses are ignored, stressing the need for stronger air pollution controls and faster reductions in coal dependency.
