Chinese solar irradiance up to 20% higher in 2025 than historical averages

Japan and the coastal regions of South Korea also recorded increases of 4% and 10% compared to LTA figures. These trends are shown in the map below, where the darker red sections of China, South Korea and Japan indicate 2025 GHI figures that are higher than historical averages.

Europe also saw increased irradiance, Solargis’ report said, with the UK enjoying its sunniest year on record. Areas of the UK recorded irradiance as much as 10% higher than LTA figures. Similarly, “most” of west and central-southeast Europe saw figures that were 4-10% higher than historical averages, and follow strong irradiance figures for northern Europe, in particular, in the first quarter of 2025.

Both of these trends are positive developments for the global solar industry considering both regions posted impressive deployment figures in 2025. In May, China passed 1TW of cumulative operational solar PV capacity, becoming the first country to do so. Europe, meanwhile, is expected to have added 65.1GW of new capacity in 2025, and while SolarPower Europe notes this is a marginal decrease from the 65.6GW added in 2024, annual solar PV additions in Europe has increased by over five times in the last decade.

“2025 has been a watershed year for the renewable energy industry and one that fills us with hope for the future, especially with solar power at the forefront of this impressive growth,” said Solargis CEO Marcel Suri. “We expect reliance on solar power to continue growing into 2026 and beyond, so it will be more important than ever to invest in the data required to understand it.”  

Lower irradiance in Southern Asia

However, Suri noted that the positive irradiance figures in some regions was matched by lower-than-average GHI figures elsewhere.

“Our analysis shows that the last year was one of extremes for solar irradiance levels: some regions experienced significantly above average levels, while others had much lower GHI than usual,” he said.

India is one of the more striking examples of this, with much of India reporting 2025 GHI figures up to 10% lower than the LTA. This effect is particularly pronounced on the south-west coast, as shown in the map below.

Solargis attributed this change to the “second consecutive year of above-normal monsoons”, which saw the monsoon season end with a 108% increase in long-term average rainfall. The company also suggested that the La Niña weather phenomenon elsewhere in South Asia caused higher rainfall, heavy floods and lower irradiance of up to 8%, compared to historical averages, in Vietnam and Malaysia.

This comes as India has significantly expanded its solar capacity additions in recent months, with the Ministry of New and Renewable Energy reporting that the first 11 months of 2025 saw a 67% year-on-year increase in capacity additions compared to the same period of 2024.

“With the La Niña phenomenon expected to persist for the rest of this winter season, we will likely see its effects exacerbate extreme weather events in certain regions,” added Suri, who has written about the impacts of extreme weather on data collection and quality for PV Tech previously.

“Extreme rainfall, floods and hurricanes present significant risks to solar projects in these regions, which asset managers need to plan ahead for if they want to keep their projects profitable in the near future.”