Most homeowners who install solar panels look forward to sunny days. It turns out, though, that power output drops when the day is too hot. Colder temperatures, on the other hand, result in more energy. And smoke from wildfires is having an even greater impact than heat and cold. 

Heat and Cold

Homeowners and businesses who install solar output often assume that knowing how much power the panels produce is easy. Manufacturers provide a number. However, that number is often based on energy output when the temperature is 77 degrees Fahrenheit. A single number doesn’t tell the whole story.

Above 77 degrees, panels produce less energy. Each one-degree increase in temperature leads to a decrease of 0.17%-0.28% in output. Since solar panels are dark-colored and installed on rooftops or racks, KC Solar mentioned, they naturally get even hotter than the ambient air. A 95°Fahrenheit day might heat the surface of the panels to more than 140°F.

The physics behind this performance drop, risk management firm Solarif explained, relates to how semiconductors behave under “thermal stress”. As silicon cells heat up, voltage output decreases faster than the current increases, resulting in a net power loss. 

Heat does more than reduce output too. It can actually degrade the panels. “Thermal cycling” causes expansion and contraction that can stress solder bonds and cell interconnections. It can also cause corrosion from moisture due to the delamination of materials.

The reverse is true in cold weather. Solar panels can perform better as the temperature drops, with energy output rising by 0.17%-0.28% for each one-degree drop in temperatures below 77 degrees Fahrenheit.

Even though the panels may generate more energy in winter, weather like ice and snow poses design and operational challenges for solar. More severe winter weather or long-term exposure to winter weather conditions can seriously disable or damage a system, the Department of Energy notes. While most snow will melt off quickly or be blown off by the wind, heavier snow or extreme weather can pose a greater risk to solar installations. During severe snowstorms, the weight of accumulated snow or ice may cause a panel to warp or even break. Snow accumulation, ice or thermal shock can also cause operational challenges.

Smoke

Along with the impacts of heat, smoke from increasingly common wildfires can have an even greater impact on the energy output from solar panels. Even if smoke does not block the sun fully, airborne particles can weaken sunlight before it reaches the panels and reduces the amount of energy a system can produce. Along with lowering rooftop solar energy output, lower production from utilities can also result in higher energy cost for homeowners and businesses. 

For example, widespread smoke from ongoing wildfires in the western United States significantly reduced solar power output across Utah and neighboring states from August 10-14, 2026, according to market intelligence firm EnergyPulse. Solar generation across California fell by up to 30 percent below forecast levels during peak sunlight hours. That lower output affected homeowners’ and businesses’ costs cost, as it affected grid operations and altered wholesale electricity prices during the typically stable midsummer period. 

The impact in New England was even greater. that electricity from solar farms in New England was 56 percent less during peak times in the week of 7-13 June than the previous week and solar power generation was reduced by a quarter in the mid-Atlantic and Midwest, according to Tech Brew.

Impacts do vary depending on location. Research at Department of Energy sites showed that even though power solar energy output broadly declined by 10%-30% statewide in California due to wildfires in September 2020, it declined by up to 58% in some places.  

Those drops can affect long-term planning, Energy Pulse noted. California and Utah, for instance, have both set targets for solar and renewable penetration, with Utah aiming for 30 percent renewable electricity by 2030. However, planners are increasingly concerned about chronic smoke reducing solar resource availability during key summer peaks. They are then looking at how to enhance grid flexibility, energy storage, and weather-resilient forecasting tools. Although solar developers are experimenting with anti-soiling coatings and higher-frequency cleaning protocols, the impact of smoke has raised new questions about the economics of large-scale solar in fire-prone regions.

It’s not just wildfire smoke that causes problems. Research led by the University of Oxford and University College London revealed that pollution from coal-fired power plants is significantly reducing the energy output of solar installations, particularly where these are expanding side by side. Aerosols - tiny particles suspended in the air - reduced global solar electricity output by 5% in 2023. The researchers estimate that about 29% of aerosol-related solar energy losses in China come specifically from coal-fired power plants.

Solutions for Solar Energy Owners

The impacts of heat, cold and smoke are significant. While it is not possible to mitigate all of the effects, some actions can reduce the impact. With proper risk management and quality assurance measures, Solarif said, temperature-related challenges can be effectively addressed to protect solar investments. On a broader basis, researchers led by Haochi Wu suggest that the risk presents a clear opportunity for the global solar industry to adapt by updating international standards for future climate realities and fostering innovation in heat-resilient PV technologies. While there is little homeowners can do now, innovation could deliver significant future improvements.