Do solar panels pose a fire risk?
Fires from solar panels are not impossible, but they are very rare. Solar panels are not even close to being on the top 10 list of causes of home fires. This list includes: cooking, heating equipment, smoking, electric appliances, candles, children playing with fire, faulty wiring, flammable liquids, Christmas trees, and barbeques.
As of 2015, changes to the California Building Code and California Residential Code require all PV systems be tested, listed and identified with a fire classification per UL 1703.
General expert opinion is that solar PV systems are at less risk of fire than any electrical equipment. Because they carry live wires, there will always be some risk, but this is negligible under normal circumstances. A very old, or very large, system will be most at risk, as will a damaged one.
There are several technical reasons for solar panels causing house fires, but most of them boil down to the same (avoidable) root: poor installation, although natural hazards such as lightning, overvoltage and power surges can also play a role. Wrongly-specified, wrongly-sized, or faulty equipment can also be to blame. Although very rare, once fire has taken hold in a solar system, it can be very difficult to resolve.
Like any other electrical installation, photovoltaic systems are subject to electrical faults such as arc faults, short circuits, ground faults and reverse currents. Faulty connections or cable insulation breakdowns can also cause problems. If these things occur, they can result in hot spots that can ignite flammable material nearby.
Another possible cause of fire is a DC arc. This is the most common cause of larger rooftop fires on commercial buildings, and can happen as a result of incorrect installation or problems in materials. A DC arc is a disconnection or fault in a current-carrying wire can cause an electric arc, which is a continuation of current flow through air, from one conductor to another, or to ground. Although arc flashes can occur with any electric installation, but solar PV systems are particularly sensitive to them because of the continuous DC current and the high currents and voltages involved. DC arcs do not self extinguish and they can reach temperatures as high as 3000°C. This is hot enough to melt metal, which can then fall and ignite nearby combustible materials.
