Solar panels are designed and rated to withstand hail storms.
Usually they are made from tempered glass and the substrate beneath is made of a flexible plastic material, making them even more hail and/or rock resistant.
Most solar panel manufacturers certify that their panels are tested to withstand hail 25mm in size falling about 23 mps. Repeated testing is done so that certification can be issued with panels prior to installation. The results vary but only slightly. Testing for hail storms is mandatory for solar panels used in Australia, so you can be sure that they have been pelted multiple times before being installed on your rooftop.
They have in the past sustained small dents or dings but again, nothing that is likely to affect the performance of the panel itself. In the US, in Denver, Colorado, once such test was conducted and the results noted that only one panel out of 50,000 solar panels tested hand an issue. That amounts to 0.1%. Not bad! In fact they discovered that the particular panel in question had been hit by multiple hail stones at once. In effect, a micro-burst.
What does all this mean to the average Perth homeowner?
It means you’ve less to worry about than you thought. While hail is possible, it is likely to cause damages to property other than your solar panels. Look at your cars, windows, roofing systems and things like that for damages. Your solar panels should hold up just fine. In fact most of the insurance losses due to hail that occur are damages other than those to solar panels.
When you are looking at systems and getting ready to install solar panels, you should check the manufacturer’s rating for the size of hailstones that your panels can endure. This is especially true if you live in an area prone to nasty hail storms.
UL does the testing for solar panels in most cases and provides standards against which manufacturers can test. They are UL 1703 and UL 61703. Standards and testing procedures are noted here: https://www.ul.com/inside-ul/solar-panels-testing/