How well do T8 fluorescent lamps maintain light output?
All lamps exhibit some reduction in light output over time. Manufacturers report light output at 40% of rated life as an indicator of maintained light output. This value is close to the average light output over the life of the lamp and is called mean light output, mean lumens, or design lumens. Figure 9 provides an overview of lumen maintenance values for T8 fluorescent lamps. Lumen maintenance is the rated mean light output as a percentage of rated initial light output. Figure 9 reports lumen maintenance for 86 presently available T8 fluorescent models from five manufacturers; data of rated mean light output were not available from the remaining four manufacturers. The data are separated by correlated color temperature (CCT), with the number of available models indicated by bubble size and labeled next to each bubble. In addition, the colors of the bubbles indicate the range of color rendering index (CRI) values to which the models belong. According to manufacturers’ data, all T8 mod
