Reply from: Brian April 18 2018, 12:46 am EDT
Unknown - have not seen any data later than 1Q2016.
Time-series data sets seen to date indicate that, for western countries, PV-related fires have rapidly peaked around 2012/2013, then rapidly decreased since. Most PV fires are from DC switches or arcing connectors.
New material and performance requirements in UL1701, UL1741, UL1699B, UL2056, UL3730, and UL62109-x seem to be providing mitigation. New code in article 690 (covered by some previous Mike Holt posts) will also provide significant mitigation.
Methinks PV as root cause will continue to diminish as a proportion, but will probably have some increases in absolute numbers as more PV systems are installed. But the big issue is how PV installations affect structural fires per the first responders; that is, their safety and ability to determine the source of the fire and control the fire.
Reply to Brian | 
The installation of large PV systems on commercial building roofs is an emerging risk due to a favorable value proposition attracting building owners to install the technology. With these systems, the likelihood of a rooftop fire significantly increases since electrical breakdown “ leading to arc faults, ground faults, and short circuits - can occur anywhere across the system. Any electrical fault can be accompanied by ensuing fire. 