Naval Energy Unit
From Elite Wiki
Naval Energy units are reputed to be far superior to standard energy units. Not generally available for retro fitting, they are occasionally found installed in new ships (often adding as much as 300,000 cr to the asking price of the standard model).
The Navy insist that they are not for sale to the public, so one can only assume that they command a very high price on the black market.
It's rumoured that the Navy may reward its Agents with these units after delivering some Thargoid Plans....