The information coming out on solar panel efficiency is really discrediting the whole premise of their use. Below freezing they collect snow and ice making them useless. During winter the cloudy conditions drop their efficiency below 43%. During summer, above 95 deg F, they lose 2% of their output for every 2 degrees F in rise.
The average home installation on the roof is 145 Deg F during full sunlight.
Lets do a little math... Panels are at 80% of their rated capacity in real life. There is always particulate matter in the air. If we have a 300w panel that means, we have 240w available in good sunlight with clean panels.
In winter we have but 42-43% on average due to ice crystals that are in the atmosphere. The average panel outputs about 100w during winter. (Low angel of incidence and ice crystals in the increased atmosphere). These panels are going to give about 32% of their rated output in winter, if they are cleaned and properly aligned.
In summer we get about 240w during perpendicular angle to the panels if they are clean. That gets reduced when we hit 95 Deg. During the heat of the day, when roof installations reach 140 deg F, those panels degrade, and the output is lowered. if we use the 1% for each 1 Degree F of temp rise, were losing about 45% of the panel output. Again, were back down in the 100w to 120w range.
The heat also destroys the integrity of the cells over time and by 10 years of service that 80% average is near 55%. Solar is not what they claim it is cracked up to be. There are three tiers of panels, and they all degrade at different rates.
Do solar panels go bad? What is a solar panel's typical life expectancy? Can you do anything to make them last longer? We answer these questions - and more.
www.solarreviews.com