Hot vs cold: What's the ideal temperature for solar panel efficiency?

Solar panel efficiency peaks at the standard test condition of 25 °C (77 °F) because voltage drops faster than current rises as temperature increases, with temperature coefficients ranging from –0.24% to –0.29% per °C for common models. However, hotter days can still yield higher total electricity due to greater irradiance and longer daylight, while factors such as wind, mounting, orientation, and cloud cover also strongly affect actual output.