You need to consider the "settings" of the pilot. My Alpha3000 below decks has setting which the helm
will respond to the slightest off course forces - a wave for example and then it corrects. If you detune this feature the helm
hardly moves at all. I am sure this reduces the current
consumption. When you motor
and like will use an auto pilot power consumption is a moot issue.
So obviously in a seaway the autopilot
will work harder and consume more power. If this is a concern (as it should be) when you plan additions to the boat then check with the various manufacturers about power consumption.
OT but on auto pilots.
I am very partial to the steering
control on the Alphas. It's a rotary knob with the 360° markings and a pointer which is the "heading" you want to steer. This is very intuitive. If you want to turn towazrd something like a buoy you rotate the know in the direction of the turn you want to make. You can do it slowly or guess the angle, but you can see when the boat has made the heading set when the helm is at center helm. If you want to tack, turn it 120° or so (depending on your boat) and it will take care of the helm and you can do the sheets! If you postion the controls where you can watch out and a turn the knob... you don't have to look at the pilot to enter the heading and so you don't have to take your "eyes off the road". I used one pilot on another boat and I had to drop my head
into the cockpit to see the display and punch in the course change as +10, -10 or +1 and -1°. That was a pain in the butt. My dial is like a mini helm.