If you set the PVWatts derate factor to 1, I expect that in the Performance Data output, Hourly Energy would exactly match the Hourly DC Output. This is not the case, and there is no clear correlation between input derate factor and the difference between Hourly DC Output and Hourly Energy. Is this a bug, or am I misunderstanding how Hourly Energy is calculated? SAM documentation specifies that Hourly Energy is the "System AC Output" and that DC Output is "DC Output of the array". Is there something besides the derate factor that relates them?