Notes: CFL = compact fluorescent lamp; COP = coefficient of performance; h = hour; kWh = kilowatt-hour; MH = metal halide; NA = not applicable; W = watt; y = year. a. Cooling energy costs assume 80 percent of input power becomes a cooling load for the halogen system, 30 percent becomes a cooling load for the MH system, and cooling load COP is 3.4. b. Lamp replacement cost assumes 15 minutes per lamp at $25/h.