The 265 mA T-8 fluorescent lamp-ballast system is a relatively recent energy-efficient lighting product. Introduced to the American market in 1982, it is now made by all major U.S. lamp manufacturers. Straight T-8 lamps have the same medium bi-pin bases as T-12 lamps, so they can fit the same sockets (this is not true for the U-bent T-8 lamps, which have different leg spacing than their T-12 counterparts). However, T-8 lamps have different electrical characteristics than T-12 lamps, so T-8s may not use a standard F40T12 type lamp ballast designed for 430 milliampere operation. The standard T-8 lamp family is designed for 265 mA operation, but T-8 lamps are also being designed to operate with special ballasts at substantially higher power levels. There is only a small cost difference between a standard T-8 lamp-ballast system and a standard F40T12 lamp-ballast configuration.
Based on efficacy alone, T-8 lamps are generally superior to any T-12 technology. A T-8 system with magnetic ballasts will typically provide 8 percent to 9 percent more light at 4 percent to 9 percent fewer watts than a system using F40T12/ES lamps with equivalent color rendering capabilities. Efficacy is further increased with electronic ballasts. The lamp cost for T-8 lamps in large commercial projects in major metropolitan areas is about the same as for T-12 lamps.