Don't know if anyone noticed this. For a weapon that mainly use power to fire, rail gun actually don't consume too much power.
Take energy-based weapons for example, small laser spent 250 power and deal 400 damage per shot. So the damage/power ratio is 1.6. Same ratio goes for ion beam (2000 damage/1250 power per second).
But if you look the number of rail gun. Say, a rail gun with 8 accelerators, witch consume 4740 power (1 launcher, 8 accelerators, and 6 ammo) and deal 12162 impact damage per shot. The ratio is 12162/4740=2.566, way more efficient than any other energy-based weapons. I am not even taking the ridiculously high penetration damage rail gun has into consideration, which would at least double the damage/power ratio.
So yeah, IMO the rail gun is OP (long rail gun only, short rail gun still suck).