One of the most effective ways to make lighting more energy efficient is to
use the most efficient lamp that is otherwise suitable for the purpose. The more
lumens per watt, the more efficient the lamp. The efficiencies for common
types of lamps are shown here.
In general, the lamp that provides the most lumens per watt will be the least expensive in the long run, due to the cost of energy. Because more than efficiency is involved, however, many factors have to be considered before an extensive relamping program is started. Some of these factors include: the type of fixtures installed and the types of lamps that can fit into them; the light output of the lamps in relation to the amount of illumination needed; the color rendering quality of the lamps; the cost of the lamps; the cost of modifying fixtures to accept a new type of lamp, and the cost of new fixtures.
In determining what type of lamps to use in a lamp retrofit program, bear in mind that manufacturers have made significant progress in recent years. More efficient lamps of the same kind as are now installed can be used in the same fixture. In addition, certain types of lamps that ordinarily require a special fixture or ballast have been made so they are compatible with another type of fixture.
Here are the efficiency figures in tabular form.
| Lamp Life and Efficiency | ||
| Life (hours) |
Lamp |
Efficiency (lumens per watt) |
| 2,000 - 5,000 |
Reflector incandescent |
7 -19 |
| 750 - 2,500 |
Standard incandescent |
8 - 24 |
| 1,000 - 3,000 |
Tungsten-Halogen |
12 - 36 |
| 12,000 - 24,000 |
Mercury vapor |
20 - 63 |
| 7,500 - 24,000 |
Fluorescent (tubular) |
41 - 91 |
| 7,500 - 10,000 |
Compact fluorescent |
50 - 83 |
| 10,000 - 20,000 |
Metal halide |
56 - 125 |
| 12,000 - 24,000 |
High pressure sodium |
61 - 140 |
| 10,000 - 18,000 |
Low pressure sodium |
100 - 183 |
