DR (Absorption) and activated abilities

A player in one of my games is building a character who can absorb attacks and use them to power his own abilities. DR with Absorption, so far so good - he's got a handful of traits he can buy/boost with the absorbed points, and it all makes sense. How would you price a trait that he has, but drains the absorbed power when used? Sort of like Costs CP, except obviously not worth the 1/5 multiplier, because it's only draining phantom points. -10%? -20%?

DR (Absorption) and activated abilities