The purpose of the panels is to power up Marine operations while reducing the quantity of fuel supply that rebels may target. There were doubts about the efficiency of the system, since it hadn’t been used in a war before.
According to Sgt. David Doty, one of the company’s squad leaders, the energy produced by the solar panels has lowered the fuel consumption of his generators from 20 gallons to only 2.5 gallons a day. Enemies blow up and fire at convoys, thus the more gas is saved by the Marines with solar power, the less they’ll have to transport.
Patrol Base Sparks can use the generators instead of using the panels, but this is not recommended during nighttime, because the enemies can spot the marines’ positions, being guided by the noise made by those generators.
The Marines also have a flexible solar panel to recharge their radio batteries. This sort of solar panel is called Solar Portable Alternative Communication Energy System (SPACES). Powershade, a photovoltaic waterproofed canvas is put on a standard tent in order to light it up. The ZeroBase regenerator, a large power source, collects enough sunlight for more than 15 computers and more than 20 lighting systems.
http://www.greenoptimistic.com/2011/01/19/afghanistan-marines-solar-panels/