http://fallout.wikia.com/wiki/Tesla_Armor_(Fallout_3) on wiki it says - "...it is a variant of the Enclave's advanced power armor MK II jury-rigged with a Tesla device that is capable of
dispersing a large percentage of the damage done by directed-energy attacks."
This would suggest that it does offer resistence against energy weapon attacks, but it is not specific to what that amount may be. As it "disperses" as opposed to absorbing the impact like most armours I think the amount of energy dispersed is an additional property and will not effect the DMG resistence stat of the armour. But as for specifics of the effect the armour has on energy weapons, I can't give you any. It has a standard 43 DR and then it's
probably 15% decrease DMG (or increased resitence) from energy weapons. It does definately give a beneficial effect to both attack and defense from energy weps, so atleast that is confirmed.
If you are specialising in energy weapons then it is definately the way to go if you want high defense. :tops: