When I deployed to the Middle East, I found large fields of nasty diesel electric generators powering our base (and many, many air conditioners) spewing out God-knows-what while requiring a constant supply of fuel. Fuel delivery costs loads more than stateside, because of security measures. However, the desert has an abundance of both wind and sunlight.
The cost scale most certainly will tip toward the renewables when accounting for the personnel and complex infrastructure needs of delivering diesel to each of these locations. Deploying renewable generation will free up military members to focus more on the mission and reduce risks and dependencies associated with foreign-sourced fuel.
Additionally, higher energy costs at semi-permanent locations should inspire efficiency measures because of quicker payback. Instead, buidings are built cheaply and with no regard to the amount of energy taken to cool them. This is a system that is tied to the generators, the security personnel, the delivery convoys, and indeed our reason for being there. A little thought toward the end use will avoid a lot of headache in fixing the input.