Under standard test conditions they will withstand hail up to one inch in diameter, traveling at 50 miles per hour. In the Northern Hemisphere, the US has its arrays facing a southerly direction with a tilt average of 35 to 45 degrees. Most Hailstorms blow in from the north thus striking the other side of the roof, or fall straight down with a glancing blow off the face. It is rare that a soft ball size hail stone will hit your panel straight on with enough force to break the glass or damage it unless it knocks it off it's support. In the case of areas of very large Hailstones it is recommended that they use thin-film (or amorphous) photovoltaic panels, which can take direct hits from rocks and giant hail with little effect. The best precaution is to have homeowners insurance in the case of any damage to your Panels. Enerize Corporation has developed a very transparent polymeric coating that can be formed with a relief or "crinkle coat" surface morphology more efficiently captures Photons over a wider angle of incidence. The polymers have a lower reflectance compared to glass. This material will also be much better suited to adverse conditions such as hail and moisture intrusion. The one thing that seems to reduce the life of the current class encased panels the most is high heat and moisture, or humidity combination over time. References: Pv-tech., Cleantech. Wiley Inter-science
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