For every degree Celsius increase above their optimal operating temperature (usually around 25°C), solar panels' efficiency declines by about 0. So, while sunny days are great for generating power, too much heat can be counterproductive. Temperature Coefficient is Critical for Hot Climates: Solar panels with temperature coefficients of -0. 30%/°C or better (like SunPower Maxeon 3 at -0. 27%/°C) can significantly outperform standard panels in consistently hot climates, potentially saving thousands in lost energy production over the. Solar panels are rated based on their performance at standard test conditions (STC), which include a temperature of 25°C. For example, if a solar panel has an efficiency rating of 20%, it means that 20% of the sunlight hitting the panel is converted into electrical energy, while the rest is reflected or lost as. Temperature has a paradoxical effect on solar panels. The basic structure of a PV cell consists of two layers of semiconducting materials, typically silicon, sandwiched together.