You're over defending. I'm at 92 AIP, 90 minutes in with 4 systems, any my "defense" consists of 20 Missile Turrets, 5-10 Sniper Turrets, 10 Basic Turrets, 10 Flak Turrets, 2 Mini-Forts, 5 Tractor Turrets. I can drop that on every one of my systems casually. I'm about to set up my choke point which comes with an Ion I and Ion IV, at which point I'll set up a real defense. Basically, the AI waves are like getting attacked by kittens. Awww, how cute, they think their so vicious. I've had zero energy problems since I took my first system and I'm running at cap for every offensive unit (I haven't unlocked any offensive units though). Spire Corvette is my bonus ship. Figured that it was appropriate given I'll be spending a lot of K and I wanted to try it out.