The long days of summer should simply mean more power. And this is mostly true – from our own data at PureSky, we see a 3-time increase in energy generation in our New York solar projects when we compare June, the month with the longest days, to the darkest month of the year, December.
But there’s a surprising twist to the story of solar: while sunshine fuels solar panels, excessive heat can reduce their performance, if they haven’t been designed to minimize the impact of it. With the increase of summer heatwaves across the U.S., understanding how it impacts our energy systems are more important than ever.
This might sound counterintuitive. Isn’t more sun always better for solar energy? The truth is a bit more nuanced. To understand how solar panels behave under different environmental conditions, we need to separate light from heat—two very different forces that often arrive together, but affect solar energy production in different ways.
More Sunlight, More Power — Usually
Solar panels work by converting sunlight—specifically, solar radiation—into electricity through a process called the photovoltaic effect. The more sunlight that hits the panels, the more electricity they can generate. That’s why solar installations thrive in sunny regions and tend to produce the most energy during the summer months when the days are longer and brighter.
But sunlight and heat are not the same thing. While sunlight is essential for production, heat is simply a byproduct of weather conditions—and unfortunately, it’s not always friendly to solar technology.
The Downside of Heat: Efficiency Loss
Most solar panels are tested and rated at a temperature of 77°F (25°C). This is considered the standard test condition used to determine how much power a panel can produce. But out in the real world, especially in midsummer or in hot climates, panel temperatures can rise significantly—sometimes reaching 113°F (45°C) or more.
The problem? Solar panels lose efficiency as they heat up.
For every degree Celsius above 25°C, a panel’s efficiency typically drops by 0.3% to 0.5% depending on the panel type (EnergySage, 2024; NREL, 2020). That may not sound like much at first, but it adds up. On a hot day with panel temperatures 20°C above standard conditions, that could mean a 6% to 10% reduction in energy output.
This is because heat increases the internal resistance within the photovoltaic cells, which in turn reduces voltage. While the current may rise slightly with temperature, the drop in voltage is more significant, leading to a net decrease in total power output (SEIA, 2023).
Hot Panels, Hot Problems
It’s not just the panels themselves that are affected. Inverters, the devices that convert the DC electricity from solar panels into usable AC power, can also suffer from reduced performance or even thermal shutdowns in high heat (Clean Energy Reviews, 2023). Similarly, battery storage systems—especially lithium-ion—can degrade more quickly if consistently exposed to high temperatures, reducing both their lifespan and capacity (IRENA, 2020).
All of this makes heat a significant factor to consider when designing and managing a solar energy system, especially in places that experience extreme summer temperatures.
Why Solar Still Shines in Hot Places
Even with the negative effects of heat, solar can still perform well in hot climates. That’s because the sheer volume of sunlight often outweighs the losses from heat. For example, the American Southwest, parts of the Middle East, and Northern Africa are some of the world’s most productive regions for solar energy—even though they’re also among the hottest (World Bank, 2022).
The key difference is in how the system is designed to handle that heat. Smart engineering and technology choices can help mitigate the impact and keep systems running efficiently even when temperatures rise.
Solutions and Innovations
As solar continues to expand, manufacturers and developers are investing in ways to combat heat-related efficiency loss. Some of the most promising solutions include:
- Passive Cooling: Simple design strategies like spacing panels apart, installing them at an angle, or elevating them off rooftops can improve airflow and reduce panel temperature (PV-Tech, 2023).
- Reflective Materials: Coatings that reflect infrared heat away from the panels can help keep temperatures down without affecting solar absorption (Nature Energy, 2021).
- Advanced Panel Technologies: Some newer solar panel types—like thin-film, bifacial, or perovskite-silicon tandem panels—are more resistant to heat and can maintain better performance under high temperatures compared to conventional silicon panels (NREL, 2023).
- Active Cooling Systems: In some large-scale solar farms, systems like water spraying or air ventilation are used to cool down panels. However, these solutions are often costly and only practical in utility-scale installations (ScienceDirect, 2022).
Climate Change and the Feedback Loop
The irony is that solar energy is one of our most powerful tools in the fight against climate change, but it’s also being affected by it. As global temperatures rise and heatwaves become more frequent and intense, solar developers and policymakers will need to plan for resilience—ensuring solar energy remains reliable even under more extreme weather conditions.
The good news is that the solar industry is already adapting. With better panel designs, smarter installation practices, and ongoing research into materials science, the gap between ideal and real-world solar performance is narrowing.
The Bottom Line of Heat and Solar
Heat may be an unavoidable part of solar energy production, but it doesn’t have to be a deal-breaker. Understanding how heat affects efficiency—and taking steps to mitigate its impact—can go a long way toward maximizing the value of solar systems.
As the planet warms, designing for temperature resilience will be just as important as maximizing sunlight. The future of solar isn’t just about chasing the sun—it’s about learning how to thrive under it.
References
- EnergySage. (2024). How temperature affects solar panel efficiency. https://www.energysage.com/solar/101/solar-panel-efficiency/
- National Renewable Energy Laboratory (NREL). (2020). Temperature Coefficient for PV Modules. https://www.nrel.gov/
- Solar Energy Industries Association (SEIA). (2023). Solar Photovoltaic Technology Basics. https://www.seia.org/
- Clean Energy Reviews. (2023). Solar inverter efficiency and thermal performance. https://www.cleanenergyreviews.info/
- International Renewable Energy Agency (IRENA). (2020). Electricity Storage and Renewables: Costs and Markets to 2030. https://www.irena.org/
- World Bank. (2022). Global Solar Atlas. https://globalsolaratlas.info/
- PV-Tech. (2023). Passive and active cooling solutions in PV systems. https://www.pv-tech.org/
- Nature Energy. (2021). Infrared-reflective coatings for photovoltaic performance under heat stress.
- ScienceDirect. (2022). Review on solar panel cooling systems for hot environments.
- NREL. (2023). Emerging solar technologies: Tandem and bifacial modules. https://www.nrel.gov/
