Derating ... its a pain. Turns out here in California temps can get up to the low teens above a 100 so add an additional 87 percent derating to the 70 percent derating and the arguement for conduit gets tough! It still makes for a much cleaner appearance if you have to pipe out to panels in the case of a service change where the panel site is changed as well. Piping romex for that last 3 feet verses thhn makes for a lot more pipes. In one recent case I was able to reduce the number of conduits from 7 to 4 -- much nicer looking!! [Linked Image]