I discovered something new as a result of a reddit comment about the power usage tallies: every ship hull has an idle, baseline power draw which isn't listed on its in-game stats screen nor, as far as I can tell, on any of the wikis. For example the Sidewinder has an idle 0.92MW power drain before any other modules.
I've filled in the values for the ships I have handy, but if anyone owns a Cobra, Type 6 or Type 7, could you plug in your current loadout and compare the power draw numbers to what you see in-game? Both the deployed and retracted figures should be off by the same amount, which is the missing baseline power draw from those hulls.