Instead of the energy system, consider the cost of military supply lines. There's more than the financial cost of delivery; long supply lines are vulnerable to attack and disruption. You don't need to imagine an example: consider IEDs in Afghanistan. Many of those were trucks delivering food and fuel to bases. Efficiency (i.e. insulating tents so less fuel is needed for A/C) results in less deliveries and less deaths.

The same principle applies at sea. Oil ships are a vulnerability and another thing to plan, as well as a major cost that can be more important than the energy efficiency issues.