A common mistake I see some people make when designing a solar energy system is that they will parallel the outputs of the solar panels without using a combiner box that has fuses or breakers.
This works fine in the “yeah, the lights come on” sense, but if you should ever have a fault in one of the modules, you may very well experience a fire at the module that will spread to any other flammable materials nearby….. yes, that means your ROOF.
Note that while the solar panel’s encapsulant and backsheet self-extinguish and only exhibit a couple millimeters of flame spread, the sheet of paper I taped to it to simulate the flammable debris that *will* gather around your panels does not! 🙂
Flammable crap you will typically find around and on your panels includes oily soot from smoke/automobile exhaust, dried leaves, paper, bird nests… anything the wind or animals can bring in!