United Listings are a US private entity that certifies various products for safety.  They certify solar panels and in the past this certification # was UL- 1703. In Europe, they have a similar entity called CE.  Recently (dont know exactly when) UL and CE came together to standardize their certification process and the new UL listing recognized internationally is now UL-61730.  This is important since clients that want grid tied systems will have the additional requirement that the utility company approve the solar panels and they require UL listing of the panels. Not all of our panels are UL listed so they can’t be used for grid tied systems.  I just received over 600 new Waaree 390w panels that have this UL-61730 listing.