Talk:Experience Mechanics/@comment-7987114-20130730134810/@comment-58.111.226.76-20131112112636

Like the guy above you said, each time you use a Warframe ability you get the exp corresponding to the amount of base energy spent.

e.g 4th skill = 100 energy == 100 warframe exp

OR

It could have been a challenge reward

e.g. Loot three energy orbs.