i received an email a couple of weeks ago alerting us that our PV array was generating less energy than typical, and that the system should be inspected. this is one of the benefits of leasing a PV system. after a quick climb to the upper roof the problem was obvious - the sedum from the green roof had grown up and over the base of most of the panels. while in hindsight it may have been better to mount the panels higher above the roof, in less than 30 minutes the sedum was cleared off and away from the panels and they were washed clean. later this fall i will prune back the sedum and again check in on the array.