Single Pack Ground Operation on B767

[Gards]

Question for engineers around. In a hot and humid climate is running air-conditioning for the whole aircraft with cargo doors open, passenger doors open, and all window shades open ie. no attempt to keep the cabin cool an overburden on a single pack controller? I was told not long ago by a captain who had no answer to this question that we are saving fuel by turning off one pack controller on the ground. To me its not saving that much if the single pack has to put out that much more air to maintain temp in the cabin.

For the small cost in savings of operating on one pack where is the tradeoff before an expensive pack controller goes tits up?

Thanks in Advance!

Gards!