Solargis Global Analysis Shows Sharp Solar Irradiance Swings in 2025

Solargis has released its annual Global Solar Irradiance Analysis for 2025, revealing significant regional deviations in solar irradiance levels compared with long-term averages, underscoring both opportunities and risks for the global solar industry.

According to the analysis, published alongside Solargis’ 2025 Global Solar Performance maps, solar irradiance in 2025 reached both positive and negative extremes worldwide. In some regions, Global Horizontal Irradiation (GHI) was recorded at up to 20 per cent above long-term averages, while other markets experienced notable declines due to extreme weather conditions.

The assessment cross-references satellite-based GHI data from the past 12 months with long-term averages to indicate how solar project performance may have deviated from expectations. The findings come against the backdrop of a record year for renewables, with more than 800 GW of new capacity added globally in 2025. Solar power accounted for nearly 80 per cent of this growth, reinforcing its central role in the global energy mix.

Solargis noted that above-average irradiance supported higher solar output in several major energy-producing regions. In Australasia, Southeast Australia and New Zealand recorded GHI levels 3 to 10 per cent above long-term norms, while parts of Papua New Guinea saw irradiance exceeding 15 per cent above average. Europe also benefited from stronger solar conditions, with the UK registering its sunniest year on record and irradiance levels around 10 per cent above average in parts of the UK and Benelux countries. West and Central-Southeast Europe saw gains of 4 to 10 per cent.

East Asia stood out as one of the strongest-performing regions. Central East China recorded irradiance levels around 15 per cent above the long-term average, with parts of the Sichuan Basin reaching up to 20 per cent. Japan and eastern coastal regions of South Korea also experienced widespread positive anomalies of 4 to 10 per cent, supporting higher-than-expected photovoltaic output.

However, the analysis also highlighted the ongoing impact of extreme weather on solar performance. In North and Central America, solar output remained stable across the US, Canada and Mexico, but Central America—including Panama, Costa Rica and Nicaragua—saw GHI levels fall 7 to 12 per cent below average due to a stronger hurricane season and increased rainfall.

In the Indian subcontinent, India experienced its second consecutive year of above-normal monsoons, with rainfall reaching 108 per cent above the long-period average. As a result, most regions recorded irradiance levels between 1 and 8 per cent below average, with parts of the southwest coast dropping to around 10 per cent below normal. Southeast Asia was similarly affected, as a strong La Niña pattern intensified the rainy season, reducing irradiance by 5 to 8 per cent in areas including central Vietnam and northwest Malaysia.

Southern Africa largely saw stable solar conditions, although parts of South Africa’s Johannesburg–Pretoria region recorded irradiance levels around 8 per cent below long-term averages.

Commenting on the findings, Marcel Suri, CEO and Founder of Solargis, said 2025 was a defining year for renewable energy, with solar at the forefront of global capacity growth. He noted that while many regions benefited from above-average solar resources, others faced reduced output due to weather extremes, reinforcing the need for robust data and monitoring tools.

Suri added that with La Niña expected to persist into the coming season, risks from extreme rainfall, floods and hurricanes could intensify in certain regions, making advanced solar resource analysis and risk planning increasingly critical for asset owners and operators.