HPS is not in a class by it self, an HPS is an HID, HID = High Intensity Discharge lamp, an HPS (High Pressure Sodium) and MH (Metal Halide) lamp are just HID's which are made for higher wattage than most lights of course, but that doesnt mean you cant use a few CFL's (Compact Fluorescent light), you can use a few CFL's that might output the same ammount of light as a 125 w MH or what ever.