Energy weapons cause your engine to overload, which will eventually cause MV and TR penalties. An energy weapon causes its DC + BV in overload points, per shot (or burst). This is modified in the following ways:
- Triple for a HYPER weapon
- Double for a BLAST weapon
- Quartered for each scale the mecha is larger than the weapon
- Halved if the mecha has a High Output engine
- The size of the mecha is subtracted from the overload at this point
Each mecha has a capacity of its size * 10 overload before it starts losing MV and TR. A large, high-output mecha can fire a Heavy Laser Cannon for quite some time, but a small mecha with a normal engine will start overheating after just a few shots of the same weapon. Each 10 points of overload over the mecha's capacity will cause a penalty of -1 to MV and TR, starting at 15 overload over capacity for a -1.
A mecha will lose 1 overload point for every 10 seconds of game-time that pass. Note that melee energy weapons will overload, too, so you'll only get a handful of swings with that energy scythe before your mecha starts boiling.