The PLT GPH450T5L4 germicidal preheated lamp operates at 21 watts. This 4 pin single ended, T5 tube emits short-wave germocidal UV light at 6.6 watts. Measuring at 18 inches in length, the germicidal lamp has an impressive life rating of 10,000 hours. Use this germicidal lamp for sanitation and purification applications. This bulb should not be used for illumination purposes.