20 watt, 4100 Kelvin, cool white compact fluorescent light bulb is an energy efficient way to light sockets once traditionally reserved for 75 watt incandescents. Compact fluorescent is lightweight, generates minimal heat, lights instantly and provides excellent color rendition. With a lifespan of 10,000 hours of using 75 percent less electricity than an incandescent, you get a tremendous energy cost savings and years of maintenance free operation. Bulb is Energy Star approved to cut back on pollution that comes from energy production.