You're right, sorry. That figure is energy output per month. Edited the post to make that clear. Added some extra statistics too from the monitoring software's report.
1000000W/mo / 30 day/mo / 24 hr/day = 1388
Is it possible my idea of "panel" is different from everyone else's? I'm counting the individual units which I purchased and which were installed on my rooftop. I suppose it's possible these units are made up of multiple actual panels, each with the aforementioned 400-500 W capacity. Not sure.