CHEAP BULBS AT WALMART OR LOWES....best to go to like a lowes or a home depo...walmart sells the 100 watt CFL's as far as i have found but i went to lowe's and they sell the 150 watt cfl.s....bout 9$ a light bulb...and for your one plant...i would say that one is enough....just a suggestion...HEY whats an HPS light???????????????