Even When Days Grow Shorter, Solar Power Stays Strong

As autumn arrives and days grow shorter, many assume PV module efficiency naturally drops. But in reality, this season often brings some of the best conditions for photovoltaic performance, especially for Europe's largest PV module manufacturer BISOL®. 

Why Summer Heat Isn’t Always Ideal for PV module efficiency 

While summer offers long days, it also brings high temperatures that can reduce module efficiency. Photovoltaic cells perform best in cooler conditions: as ambient temperature drops, electrical resistance decreases, allowing the module to operate more efficiently.  

Photovoltaic cells perform optimally between 15–25 °C, as each 1 °C rise above 25 °C typically reduces output power by about 0.29 %.  

In simple terms, cooler air helps the module convert sunlight into electricity more effectively, producing slightly less current and substantially more voltage, maintaining higher overall performance than in the heat of summer.  

Lower cell temperatures reduce semiconductor resistance and increase the open-circuit voltage (Voc), which directly enhances power conversion efficiency. 

Autumn Light: A Perfect Balance 

At the same time, autumn skies create a perfect balance of light. Autumn conditions feature a higher share of diffuse irradiance, maintaining stable power even under partially cloudy skies. White clouds scatter and reflect sunlight, increasing diffuse illumination that modules can still absorb from multiple angles. The sun still stands relatively high in the sky, and the days remain fairly long, providing steady exposure without the excessive heat of midsummer. This combination of cooler air, bright reflected light, and balanced sun angles allows modules to operate close to their optimal efficiency, day after day. 

Designed for Year-Round Excellence 

Together, these natural factors make autumn an ideal time for reliable and efficient solar generation. BISOL modules are designed to make the most of these conditions. Engineered with outstanding low-light performance and excellent temperature coefficients, they continue to deliver high yields even under overcast skies and in cool, variable weather. 

Installer-Focused Technical Highlights 

For solar professionals, BISOL modules offer installation and performance advantages that make every season profitable: 

• Power Temperature Coefficient: As low as -0.29%/°C, minimizing performance loss in hot climates and maintaining high efficiency in cooler conditions. 

• Low-Light Optimization: PV modules maintain high output in diffuse light, ideal for autumn and spring conditions. 

• Mechanical Load Resistance: Certified to withstand up to 7.000 Pa snow load and 2400 Pa wind load, suitable for rooftops in alpine and coastal regions. 

• PID-Free Guarantee: 100% PID resistance enhances long-term system stability, reduces degradation, and lowers maintenance costs. 

• 25-Year Product Guarantee & 25–30-Year Linear Performance Guarantee: Peace of mind for installers and clients alike. 

• 100% European Manufacturing: Fully in-house production with strict quality control ensures consistent performance and full traceability. 

• Installer Support: BISOL offers technical documentation, mounting guides, and responsive support for on-site troubleshooting. 

Built to Endure Every Season 

Each module is built to last, rigorously tested for mechanical strength, temperature cycling, and real-world endurance. Whether it’s summer heat, strong winds, winter snow, or the transitional beauty of autumn, BISOL ensures consistent energy production and long-term reliability. 

Smarter Solar Starts Here 

So as the leaves turn and the air cools, remember: shorter days don’t mean less solar power. They mean smarter solar performance. Because energy saving starts with choosing modules that deliver in every season.