> My trips tend to be a fair amount of driving and I do have an aux battery
> setup, so I usually run off 12V and only switch over to propane when
> camped.
>  Why use propane when the battery power is free.

You don't get free energy from your battery.  It comes from your
gasoline because your engine has to work harder turning the alternator
because the battery needs more recharging.
  Here in Illinois we now have a law that your headlights must be on
whenever your wipers are in use.  When the law was first enacted, one of
the legislators was quoted as saying that it doesn't cost anything to
have your lights on....Oh well.  Perhaps better science education would
help.  Unfortunately they recently changed the science teaching
certification categories here so that biology teachers are now
considered well qualified to teach physics and vice versa.  This helps
meet the Federal requirements for NCLB.

Larry A.
got fed up and retired from teaching