There are a variety of reasons to practice group relamping, in which a set of lamps is replaced at a scheduled time, rather than spot relamping, in which lamps are only replaced when they burn out. Most of these reasons apply to fluorescent and high-intensity discharge (HID) lamps rather than incandescents, which have much shorter lifetimes.
Economic comparisons typically show that group relamping has higher lamp costs but lower labor costs than spot relamping. One such comparison in Table 1 indicates a 31 percent overall savings from group relamping. This type of calculation is heavily dependent on the difference in labor costs between group and spot relamping. For example, if the group relamping cost of $1.50 per lamp jumps to $3.50, the balance tips in favor of spot relamping. General Electric provides a free online calculator that provides estimated savings from group relamping based on average lamp life, annual operating hours, and total number of lamps. Remember, however, the noneconomic benefits of group relamping discussed above when deciding between the two methods.
|Relamp cycle (hours)||Average relamps per year||Average material cost per year||Average labor cost per year||Total average cost per year|
|Spot relamping on burnouta||20,000||525||$1,391||$3,150||$4,541|
|Group relamping at 70% of rated life)b||14,000||750||$1,988||$1,125||$3,133|
|——————— —————— ——————— —————|
a. Assumes labor costs of $6.00/lamp for relamping and cleaning, material cost of $2.65/lamp, and 3,500 hours/y operation.
b. Assumes labor costs of $1.50/lamp for relamping and cleaning, same material costs and operating hours as for spot relamping.