6000xp is not UL9540 certified. YOU CANNOT LEGALLY install in the US along with solar panels. 

I have 4 6000xps connected to 2 EG4 power pro batteries. Was trying to get permits in Phoenix, AZ and learned that this is not a legal configuration due to it not being UL9540 certified. YOU CANNOT LEGALLY install with in the US along with solar panels. The more expensive 18k is UL9540 certified, but will be calling the city to confirm before trying to return these.