India Sees Below-Average Solar Resource in 2025: Solargis

India experienced a below-normal year for solar resource availability in 2025, with most parts of the country recording lower-than-average solar irradiation due to an extended and intense monsoon season, according to an annual assessment by Solargis. Singapore-based Solargis leverages satellite image processing and atmospheric and meteorological models for solar-related data. 

Data from Solargis’ Global Horizontal Irradiation (GHI) anomaly maps show that solar radiation across India was between 1% and 8% below long-term averages during the year, with the steepest declines along the southwest coast, where anomalies reached nearly 10% below normal.

East Asia In Contrast

The weaker solar resource conditions contrast sharply with trends in East Asia, particularly China, where some regions recorded exceptionally strong solar irradiation, highlighting growing regional divergence in weather-driven solar performance.

Solargis publishes its GHI anomaly maps each January to assess how annual weather patterns deviate from long-term climatological averages. The maps are widely used by project developers, asset managers and investors to evaluate year-on-year photovoltaic (PV) performance and climate-related risk.

Globally, 2025 was marked by extreme variability. While several regions posted strong gains, others recorded significant shortfalls. In some parts of the world, solar irradiation rose as much as 20% above long-term norms, prompting Solargis to expand its standard anomaly scale to accommodate unusually large deviations.

India Impacted by Prolonged Monsoon

In India, the primary factor affecting solar resource availability was an unusually long and intense monsoon season. Persistent cloud cover and higher rainfall reduced irradiation across key solar-producing regions, reinforcing concerns around increasing inter-annual variability linked to shifting monsoon patterns.

Analysts note that while India’s installed solar capacity continues to expand rapidly, changing weather dynamics are making accurate yield forecasting and climate-adjusted planning increasingly critical for developers and lenders.

China and East Asia See Exceptional Year

In contrast, East Asia emerged as the strongest-performing solar region in 2025. Central and eastern China recorded GHI levels around 15% above long-term averages, with parts of the Sichuan Basin reaching gains of up to 20%. The region has now posted above-average solar resource conditions for four to five consecutive years, benefiting large-scale PV operators.

Japan and South Korea also saw a strong year, with irradiation typically 4% to 10% above normal in several regions. These gains coincided with record summer heatwaves, which further boosted solar output.

Mixed Trends Elsewhere

Outside Asia, much of Western, Central and Southeastern Europe experienced a sunnier-than-average year, with GHI levels generally 4% to 10% above long-term norms. Southeast Australia and New Zealand also recorded positive anomalies, supporting stronger-than-expected PV generation.

By contrast, Central America saw some of the sharpest declines globally, with solar irradiation falling 7% to 14% below average, largely due to an active hurricane season and heavy rainfall. Negative anomalies were also observed in parts of Southeast Asia, southern Africa and western Russia.

The findings underscore the growing importance of climate variability in shaping solar power outcomes. For India, 2025 serves as a reminder that long-term capacity growth must be matched with increasingly sophisticated weather risk assessment and resource forecasting, even as other regions benefit from unusually favourable solar conditions.