Banshee's sound quake

[(PSN)the_name_is_matt]

For some reason I have noticed that whenever I use this ability that it will require me to have more energy that needed say the actual cost of ability is 25 and I have 500 energy instead of my energy dropping to 475 once activated it will drop way below that and then go back up to 475 I don't quite understand why this is happening which is causing me to not be able to use the ablities properly