How does solar panel efficiency vary with temperature?

Solar panels produce less electrical power as their temperature rises because the semiconductor physics that convert sunlight into current become less favorable at higher temperatures. Observations and module datasheets reported by the National Renewable Energy Laboratory and analyses by Martin A. Green at the University of New South Wales document that most crystalline silicon modules lose roughly four tenths to five tenths of a percent of power for every degree Celsius above the standard test condition of twenty five degrees Celsius. Fraunhofer Institute for Solar Energy Systems notes that some thin film technologies such as cadmium telluride and certain copper indium gallium diselenide variants show smaller absolute losses per degree, which makes technology choice relevant for hot climates.

Physical causes
Two main semiconductor effects drive the temperature dependence. First, the semiconductor bandgap narrows as temperature increases, which lowers open circuit voltage and reduces the maximum power point. Second, carrier recombination and series resistance behavior change with heating, further reducing current at useful voltages. These mechanisms are well established in semiconductor physics and are reflected in the temperature coefficients manufacturers publish on datasheets. Module testing protocols referenced by the International Electrotechnical Commission and by testing laboratories report a module nominal operating cell temperature that is commonly tens of degrees above ambient under sunlit conditions, so modules rarely operate at the twenty five degrees Celsius used for standard efficiency ratings.

Practical consequences and regional nuances
The practical consequence is that a panel array in a hot, sunny region will produce less energy than implied by standard efficiency numbers. If a crystalline silicon module with a temperature coefficient of minus four tenths percent per degree operates thirty degrees Celsius above the standard reference, energy output can drop on the order of twelve percent. The National Renewable Energy Laboratory provides modeling tools that incorporate temperature coefficients and realistic operating temperatures to predict annual energy yields. For communities in deserts, tropical coastlines, and certain urban settings the combination of high ambient temperature, heat island effects, and strong irradiance means designers must account for temperature losses when forecasting generation and estimating payback periods.

Design and mitigation
Engineering responses include improving module ventilation with mount spacing, selecting technologies with better temperature coefficients, using light-colored roofing or mounting to reduce absorbed heat, and in some utility or industrial installations adopting active cooling. Bifacial layouts and elevated trackers that promote airflow can recover some losses by lowering module temperature during critical production hours. Cultural and territorial considerations show up in deployment choices; regions with limited water resources must weigh the benefit of water cooling against scarcity and cost, while dense urban installations often trade slightly lower efficiency for rooftop space optimization.

Manufacturers and testing labs provide temperature coefficients and nominal operating cell temperature figures that should be used when moving from laboratory efficiency to expected field yield. Incorporating those numbers into project economics and grid integration planning yields more reliable performance estimates as climates warm and systems age.