Cost isn't everything...but I remember hearing that the effective diesel cost in a war zone was something like $400 dollars per gallon. I think that was probably more than 10 years ago, and probably related to Afghanistan or Iraq. Additionally, there are a whole bunch of people at risk every time a tanker of fuel has to drive out to the war zone with a protection detail.
If, for example, you only had to haul out a system of solar panels and batteries once to a forward operating base, then the savings (in both $ and human risk) could be considerable.
Obviously, tons more considerations and logistics that would need to be worked out...and it's not going to work for ALL of the needed vehicles. But, if any of those vehicles can reasonably be swapped to electric, then there could be some advantages, cost savings, and human risk reduction.