Ive thought about that often.

It comes down to this:

Fuel conception increases on how many RPM's your engines are doing. Higher RPM's, more fuel consumed.

With that in mind, you have two scenarios:

a.) Running at ahead slow using diesals for 24 hours. I think you do about 100 or 200 RPM's at ahead slow, on each engines.

or

b.)Recharing your batteries at ahead slow for a 4 hour period. While recharging, ONE engine will be at 500 RPM's, the other that is propelling the boat will be at 100 to 200 RPM.


This delimna i answered for myself the hard way. Long story short, a patrol to GR89, i was just short of fuel to make the round trip without a milk cow. By only running the diesals 4 hours a day to recharge batts, i had enough fuel to make the trip. IF i had cruised on the surface the entire time, i wouldn't have had the fuel.

Ive never felt comfortable running on my batteries. I wasnt sure if I was burning more fuel that way or not. Im going to run into some real problem in another year or two when the air traffic increases.