The energy drain effect is not the same as energy drain.
The abilities from in the Energy Drain tree(Surge, Life Steal and Nova Bomb CD reduction) only trigger from the Energy Drain ability(ie. Using your melee ability).
The energy drain effect is the reduction in your grenade cool down.
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see im thinking that might be the case too, in which case i would say that this skill is useless, i dont need another cooldown for my grenade, i think by comparison to the sunsinger skills, the double grenade sunsinger gives you is far better than embrace the void, i think this is an error, it would make more sense if it also gave you the secondary ability of energy drain.