I did most of the installation myself, but lacked the expertise and required license to do the final electrical connection, so I asked KT solar if they could do it. They responded right away, and did everything they promised and beyond. It turned out there was a manufacturers defect in my inverter, which they found while running the startup tests. They called manufacturer directly, arranged for a replacement part, and took care of everything. My system has been working perfectly after that, and my electric bill is actually less than zero.
Note that my bill is so low only because my provider (Green Mountain) pays me the same rate for the power that I supply to the grid as for the power that I receive from the grid. There are not many providers offering this deal.