Proper reflectors, light movers, and reflective material on walls greatly increases intensity
and efficiency of these lights.
Most high intensity lights can be run with either 120 volt (standard house current),
or 240 volt (e.g. used for electric dryer).
Electricity cost would be the same but the latter would draw half the amps allowing the grower to run twice as many lamps on the same electrical circuit.
Light timers are available for either voltage but always check to see that the amperage rating on the timer exceeds that of the lights.