- The 'Max consumption' value listed in a building's tooltip is the amount of power it will use when operating constantly
- An inserter moving items from chest to chest is as constant an operation as it gets (assuming the source chest always has items and the destination always has room)
I tested other arrangements, too. The highest power demand I could find was for moving items from a saturated yellow belt into a chest, which had an average power usage of 114kW - still much less than the tooltip value. (Curiously, having the inserter drop items onto a belt majorly reduced the power requirement. Once the hand was in position, power usage dropped to 1kW - i.e. idle - until all items had been dropped on the belt. I have no idea why dropping items in a chest costs 169kW while dropping them on a belt it free.)
While it makes sense that an inserter's power usage would be different for different actions, such as picking up items, rotating, extending, and dropping, and using less power isn't a bad thing, this makes the inserter 'Max consumption' statistic useless for any sort of planning purposes.