ITER requires a steady power of 125 MW during back-to-back nominal pulse operation, predominantly for cooling water, cryoplant, and buildings (HVAC). About 6 MW must be provided in the case of loss of off-site power, and diesel generators will be used. Systems needing continuous power will incorporate uninterruptible power supplies in their design.

Pulsed power for the magnets (the central solenoid, poloidal field, and correction coils) and the plasma heating system needs to be delivered in addition. For the generic site this is assumed to be provided directly from the local electricity network, although requirements can be reduced for a particular site if necessary by purchasing extra energy storage. Typical requirements for active (P) and reactive (Q) power for the nominal pulse are shown below. The high level of reactive power means that a reactive power compensation system needs to be used. This system, composed of harmonic reactive power and high frequency filters, brings the reactive power level to 400 Mvar. Active power is limited to 500 MW peak with a peak derivative of 200 MW/s and maximum step changes of 60 MW. In the case of plasma disruptions the system is designed for the necessary rapid power shedding to achieve this.

More information can be found in the ITER Technical Basis .