The US Navy's railgun project is honestly at the forefront of weapon development right now. Energy requirements are absolutely no problem with the prevalence of nuclear reactor-fitted warships using this. A nuclear reactor aboard a modern warship won't even notice the firing of this weapon.
What this weapon does bring is strength, reach, price and safety. The projectile's impact is comparable to a cruise missile strike, but is significantly cheaper. It has extreme potential for long-ranged damage and fair precision and on top of that, there is no need to waste large amounts of space storing explosive propellant base weaponry like there are today.
The only real concerns for the project are apparently cooling the rails and wear and tear on the rails.