Bought to work with the 5x100W solar panels I bought here. Obviously I could go higher and probably will go higher. So far there are no problems with this item. That works great. Easy to use, instructions are easy to read and follow. This is my first MPPT but probably the 5th solar controller. I definitely find it more efficient. I installed my panels in parallel to take advantage of the higher voltage you get. The maximum solar panel voltage of this controller is 170V, which is higher than that of the market controller (150V), which is more efficient. than what I have used or seen.