New research led by the University of Oxford and University College London (UCL) has revealed that pollution from coal-fired power plants is significantly reducing the energy output of solar photovoltaic (solar PV) installations, particularly where these are expanding side by side. The findings have been published in Nature Sustainability.

Global scale of solar power losses
The new study mapped and assessed more than 140,000 solar PV installations worldwide using satellite data. By combining this with atmospheric data on air pollution, the researchers calculated how much sunlight is lost and how this reduces electricity generation.

They found that aerosols—tiny particles suspended in the air—reduced global solar electricity output by 5.8% in 2023. This is equivalent to 111 terawatt-hours (TWh) of lost energy—the amount generated by 18 medium-sized coal-fired power plants.

Crucially, these losses represent a significant and often overlooked constraint on the clean energy transition. Between 2017 and 2023, new PV installations added an average of 246.6 TWh of electricity each year, while aerosol-related losses from existing systems reached 74.0 TWh annually—equivalent to nearly one-third of the gains from new capacity.

This highlights a previously unrecognized interaction between fossil fuel use and renewable energy, where emissions from one system directly reduce the performance of the other.