Ventilation / Panel Temperature

The performance of all Solar PV panels drops the hotter the panel gets, with most panels (including our value and standard system panels) losing around 0.45% power output per degree C they rise above 25^oC. In peak sunlight the panels can reach temperatures of 50-60^oC or higher, resulting in a performance loss of 10-15%, or higher, if there's little wind to cool the panels.

Sanyo's HIT panels in our Ultra Efficient systems also have much better high temperature performance than most panels, as their performance only reduces by 0.3% per degree C, meaning their high temperature performance is roughly 33% better than standard panels.

The performance loss at higher operating temperatures in peak sunlight is the main reason that Leeds Solar's XL systems make sense, as a standard 4kWp will rarely actually produce an output of more than 3.3-3.4kW for longer than a few minutes, whereas a 4.5kWp system would naturally run at an output of around 3.7-3.8kW AC in peak sunlight levels. It will also obviously produce around 12% more energy all day, every day when the sunlight levels are lower.

The need for ventilation to reduce the panel operating temperatures is the reason that solar PV panels are almost always mounted on rails above the roof surface, instead of being integrated into the roof as solar water heating systems often are.