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					</table>Solar generation depends on the solar irradiation that falls on photovoltaic panels. India has witnessed up to 7% below-average solar radiation variability between 2018 and 2022 and between 3% and 10% in 2024.
Slovakia-headquartered <a href="https://solargis.com/" target="_blank" rel="noopener">Solargis</a> is an online platform with solar design, energy simulation, data analytics, and solar and meteorological data to support various stages of solar power projects. In this interview, Solargis’ CEO Marcel Suri speaks about the impact of a drop in irradiance on solar project performance, his company’s solutions for the solar industry, and forecasting technology trends.
How do Solargis’ solutions help the industry design solar photovoltaic projects?
At Solargis, we offer an online platform that includes solar design, energy simulation, data analytics, forecasting software, and accurate and validated solar and meteorological data to support every stage of solar power projects, from pre-feasibility and planning to operation and management.
On the project design side, we recently launched Solargis Evaluate 2.0, a new cloud-based solution that integrates high-resolution solar and meteorological data, a 3D energy system designer, a photovoltaic (PV) components catalog, reliable energy yield simulations, and analytical reporting.
As the solar industry scales to meet global demand, project evaluation has grown increasingly complex due to evolving financial, technological, and climate-related risks. Tackling this complexity requires advanced, data-driven, and verifiable modeling approaches that challenge outdated industry standards. This solution is what Evaluate 2.0 aims to provide.
What have been the historical trends in irradiance levels in India?
Climate science is a highly complex field, so without robust evidence from a full and rigorous scientific study, it would be misleading to talk about long-term historical ‘trends’ such as a decline in solar irradiance.
Solargis radiation data shows that the Indian solar market has been considerably impacted by resource variability in recent years.
In 2022, we published a 10-year solar performance study highlighting how solar irradiance levels have deviated from the long-term averages often used to underpin production estimates and financial models.
We found that India experienced solar radiation variability, with up to 7% below average across the subcontinent between 2018 and 2022. This variability validated our concerns with PV asset managers about lower-than-expected irradiance levels.
More recent research published last year showed that in 2024, most of India experienced a dip in solar radiation between 3% and 10%, marking another year of below average solar resources.
What factors are behind the lower irradiance levels in India in recent years?
Several factors have contributed to the recent decline in solar irradiance in India. The first is extreme weather. In 2024, the monsoon season was among the wettest in recent years, with rainfall exceeding the long-term average by nearly 8%. While beneficial for agriculture and water reservoirs, this had a negative impact on solar energy production.
Another key factor is poor air quality caused by increased pollution. Solargis research published in April last year found that air pollution has significantly impacted India’s solar industry, especially during winter. In January 2024, Northern India experienced some of the poorest air quality in decades, with persistent fog and smog lasting up to 20 days in some areas.
High aerosol levels have had a direct effect on PV performance. Our Global Horizontal Irradiance map for January 2024 showed substantial drops of between 30% and 50% compared to the long-term average.
These reductions were particularly notable around highly developed areas, where aerosols and cloud cover further limit resource availability. If not accounted for during project development, such conditions can cause underperformance and erode investor confidence in one of the world’s fastest-growing solar markets.
Which regions in India have witnessed lower-than-usual irradiance?
In 2024, most of India experienced a decline in solar irradiation of 3% to 10%. The monsoon season was particularly intense, exceeding the long-term rainfall average by nearly 8%.
This development led to prolonged periods of cloud cover, especially in regions like Central India and the Western Ghats, and caused reduced irradiance availability. Key solar hubs like Gujarat and Maharashtra also recorded extended below-average solar radiation, making it clear that project developers in these areas must factor in more significant resource uncertainty.
What has been the impact of the drop in irradiance on solar generation in the Indian context?
Solar radiation closely correlates with energy generation over longer time frames, such as a month or a year. Generally, a 5% decline in solar radiation typically results in a similar 5% drop in electricity generation. This relationship is largely linear, especially when data is aggregated over time.
However, the actual impact on generation can vary depending on a PV project’s specific design and configuration. Factors such as the ambitious DC/AC ratios, the use of tracking systems versus fixed structures, and the overall system design can influence how sensitively a plant responds to changes in irradiation levels.
What tools does Solargis employ to monitor irradiance levels? How does satellite monitoring compare with on-ground monitoring?
Developing large-scale solar projects requires access to long-term solar and meteorological data – ideally 20 years or more.
Satellites and meteorological models are global and offer extensive coverage, tracking parameters such as clouds, aerosols, air temperature, and wind. However, their spatial and temporal granularity may not capture local climate variations, especially in areas with complex terrain or near cities, large industries, and coastlines.
For this reason, satellite data and models should be complemented with ground-based, site-specific measurements, ideally taken over at least one year. This hybrid approach – that we at Solargis apply – enables developers to validate long-term trends and better reflect the actual environmental conditions on-site.
What are the latest trends in forecasting technologies? With the evolution of artificial intelligence (AI) and machine learning (ML), can we expect more accurate predictive models?  
Yes, especially when AI and ML are applied to solar radiation forecasting, which is the primary source of error in solar power forecasts.
Traditionally, forecasts have relied on numerical weather prediction models, and some providers also use satellite-based cloud motion vector models.
What’s changing now is the smarter integration of these models using AI and ML. These technologies allow us to refine forecasts by learning from past errors and dynamically weighing inputs based on ever more input data. They’re particularly useful for predicting extreme weather events, such as dust storms or high winds, which can significantly affect the power project’s output.
By improving the accuracy of forecasts, AI- and ML-enhanced models allow solar operators to make more informed real-time decisions and minimize deviations from the expected generation.
To what extent have Indian solar companies adopted irradiance monitoring technologies?
Solargis has supported Indian solar companies for many years. Our customers prioritize dependable irradiance data to address performance variability.
For instance, companies use Solargis’ real-time datasets to improve forecasting and operational monitoring. Solargis provided them with high-quality, one- and five-minute resolution data. This data-sharing enabled more accurate ground measurement verification and project optimization – from design to operations.
Some companies are also integrating advanced technologies such as bifacial PV modules, intelligent trackers, and storage. Our partnership with them ensures they have the data to predict performance confidently.
How does Solargis help the solar industry cope with extreme weather events?
The growing frequency of extreme weather events makes access to granular, historical, and real-time data more essential than ever.
Solargis helps developers from the early project stages by offering access to 26 years of high-resolution irradiance data, helping them understand interannual variability and assess long-term resource risks.
We also offer real-time and forecast datasets that enable more accurate asset performance evaluation and proactive operational decisions and help reduce the financial impact of weather and technology underperformance. Our advanced modeling and data products are designed to improve system resilience, accuracy, and overall project bankability in an increasingly volatile climate.

Most of India Saw 3-10% Decline in Solar Irradiation in 2024: Interview

India has witnessed up to 7% below average solar irradiation in the last four years, reflecting the concerns of local asset managers about a decline in irradiance levels, according to global solar data assessor and forecaster <a href="https://solargis.com/" target="_blank" rel="noopener">Solargis</a>.
According to the Solargis irradiance map, factors like aerosols and cloud cover had impacted resource availability, and this could result in solar farms underperforming, impacting investor confidence in one of the world’s fastest-growing solar markets.
Solargis highlights that the challenges in performance can be addressed with investment in robust resource data throughout the lifetime of every solar project. Such an investment will help developers monitor irradiance levels and deploy changes in the plant like hours of sunlight, satellite-based solar radiation data capture, and solar storage options.
Intelligent resource investment
The Solargis report highlights intelligent resource investment to study factors leading to a decrease in irradiance in India. For instance, the data retrieved from ground-mounted sensors were prone to errors due to shading, irregular or insufficient cleaning of panels, misalignment of instruments, and calibration issues.
A satellite-based approach to monitoring irradiance allows for quality control and error detection and helps calculate the performance ratio (PR). A satellite-based resource is beneficial to developers with a smaller portfolio.
Another smart resource investment in studying irradiance would be pyranometers — a device that gives information about solar irradiance in particular geography by measuring the flux density in solar radiation. The installation and maintenance of a pyranometer are relatively expensive and more practical when used in large-scale solar projects.
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Referring to the varying irradiance levels impacting the generation capacity of solar projects, the CEO of Solargis, Marcel Suri, observed, “Controlling the weather is outside of our capabilities, but what solar developers, owners, and operators can control is their knowledge. Vital, trusted intelligence on the solar resource, albedo, and specific geographical conditions at project sites can be the difference between an asset that retains its value throughout its lifecycle and one which fails to live up to its potential.”
The Solargis report also highlights that globally, long-term averages set by solar developers remain deviated due to the variations in irradiation levels. It states that India, North America, and Australia are three such global economies that face challenges posed by varying irradiance levels, ultimately slowing down power production in solar plants.
The last five years of maps in Australia show significant irradiance variations throughout the continent compared to long-term averages. The fluctuating weather conditions were extreme during 2019-2020, leading to the disastrous bushfire ‘Black Summer’ in Australia. Solargis is now analyzing the long-term data to understand climate drivers like El Nino and La Nina.
The above-average recordings in the northwest of North America reflect anomalies such as the recent heat dome, which witnessed the temperature peak at a record high of 49.6 degrees Celsius. The Solargis maps show below-par irradiation in the north and southeast America compared to the last decade’s averages versus long-term trends. According to Solargis, the long-term data-driven approach will help asset owners in North America ready their solar projects to withstand variable weather conditions. It will also be crucial as the Investment Tax Credit (ITC) phases out, impacting long-term revenue security.
To track the irradiance levels, a research team from the <a href="https://home.iitd.ac.in/index.php" target="_blank" rel="noopener">Indian Institute of Technology</a> (IIT), New Delhi, <a href="https://mercomindia.com/iit-delhi-researchers-develop-portable-solar-tracking-towers/" target="_blank" rel="noopener">developed</a> non-mechanical solar tracking towers with highly reflective mirrors, vertically mounted in a particular way that they fall in the line of the sun during different phases of a day. The team found that the deployment of mirrors enhanced the irradiance on the solar photovoltaic panels during the entire day. The solar irradiance increased by more than 50%, resulting in 20-25% more power generation than solar panels with conventional mounting techniques.

India Witnessed Up to 7% Below Average Solar Irradiance in the Last Four Years: Report

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