Hi,
Does setting input use less power than ADC? I think I've noticed an uptick in power when reading a pin.
Compared with what? Sleep or "normal" running?
AFAIK there is no significant (additional) power drain associated with taking an ADC reading. The FVR (which can be used as the ADC Reference) does of course drain some power when it's enabled.
However, it is "well known" that a digital input can drain more power (from the supply rail) if it is NOT receiving an input voltage close to either Vss (Ground, Logic 0) or Vdd (supply, Logic 1). Thus, it's often suggested that "unused" digital inputs should be tied to ground (preferably with a resistor), although my preference is to just enable the "Weak Pullup" resistors on any unused digital inputs (if power drain is a major concern). But if any particular inputs are receiving an "analogue" voltage (i.e. away from Vdd or Vss) then you should NOT declare them as (digital) inputs, but as an ADC input, to keep the power loss lower.
Cheers, Alan.