sEWaRk? Where's that at?

 

On topic, during the first Iraq encounter I remember the airline issuing a directive to not start APUs 10 minutes before departure. So by my own very limited recollection, a lot of when to start the Apu versus gpu was due to the price of jet a at the time.

Yes, it is a factor. Basically, airline compares the ground power prices, fuel prices, and decides which one is better.

 

Also if you want to be a bit more technical, factor in differences in airports, the cost of having different procedures per airport (small, but real), and eventually you will come to what the airline beancounters look at to decide what is the best for this or that airline.