I've had both wheel (on my last boat) and my present tiller.. With the
wheel, I found that once I had the boat balance properly the AP use very
little current.. I went to Baja with it for both motor sailing and sailing
and never had any problem with the power drawn..

If your situation requires more then maybe increase your battery bank size..

But then, if you are only using the AP while motoring, why would you be
concerned since the engine is charging..

Steve
s/v Good Intentions