A lot of energy, yes, but for a very short period of time.
Given that the cost of the entire prototype program is vastly less than the cost of a Shuttle launch, it is safe to assume(!) that the per-kilo cost to orbit is substantially less via railgun.
In addition, given that the payload is launched by a single initial impulse rather than a long, slow burn, the mass fraction is much higher. You are not using energy to lift a bunch of fuel to provide energy to lift a bunch of fuel to provide, etc., etc. to lift the payload into orbit, you are simply lifting the payload into orbit.
Viable payloads for this technology include food, water, fuel, oxygen, metal, plastic. With appropriate facilities in orbit, these things can then be assembled into useful and interesting devices. If all we have to do is lift astronauts and sensitive components via Shuttle (or Proton rocket or Dragon capsule or whatever), then we can save billions on launch costs while exploring our solar system.