The Duet itself draws a trivial amount of power, compared to the Nozzle Heater, Fans, etc. The bed also draws a lot, and I didn't mention it because it could be on the same power supply, or separate.
When I say "Trivial", think of a drop of water in an entire cup.
Another way to phrase: Calculate for your heaters and fans. Allow a good "margin" or "pad" (because power supply ratings are often optimistic), and don't worry about the current for the board itself.
