Long lamp life cuts investment and maintenance costs. "Life" is defined in different ways: "average service life" is the yardstick used for thermal radiators such as incandescent lamps and halogen lamps, "economic life" for discharge lamps.

Average service life

The average service life of a lamp is the number of hours for which a lighting installation operates before 50 percent of the lamps fail. Apart from incandescent lamps (approx. 1,000 operating hours), it is also used for halogen lamps (approx. 4,000 operating hours), low-voltage halogen lamps (approx. 4,000 operating hours) and energy-saving lamps (with integrated EB approx. 15,000 operating hours).

Economic life

The economic life of discharge lamps is significantly longer. Where electronic ballasts (EBs) are used, it is longer still: 16 mm diameter fluorescent lamps, for example, reach 20,000 operating hours. Economic life is the yardstick used for fluorescent and compact fluorescent lamps with pin base, induction lamps and high-pressure discharge lamps (metal halide lamps, high-pressure sodium vapour). It takes account of not only failed lamps but also the reduction of luminous flux in a lighting installation after a specific number of operating hours. This must not fall below a specified minimum value.