It has no power bonus, only the ability to transwarp to most sector blocks in the game. The description is muddled because at one point it was going to have a console of its own but this wasn't added so the ship remains as it always has. Only the T3 version has the console with the power bonus.

The C-store hook is get you go buy both the T3 and the T5 Excelsior. Then move a Transwarp Computer Console from the T3 and into your T5. Effectively gaining the passive bonus to Starship Warp Core Efficiency that scales with level as well as reducing the recharge time of all Transwarp travel abilities.

You can move the console and then dismiss the T3 if it's taking too much room in your shipyard.