Use of task lighting can reduce the footcandle levels in a space and lower the electrical energy demand by 20 to 50 percent. Areas to consider for this project are large open office areas where each workstation has a desk lamp, such as an engineering office that provides each drafting table with a lamp. Here, the overhead lighting is no longer used to provide a task-specific illuminance but serves only to supplement local light sources at each desk.
Light levels can be safely reduced in noncritical areas such as hallways, lobbies, waiting rooms, storerooms, mechanical rooms, and restrooms. There are many ways to reduce the illumination levels. The energy saved is in direct proportion to the reduction in wattage.
A favorite way to reduce illumination levels is to merely remove lamps from the fixture. This certainly does diminish light output, but the ballast continues to use the same amount of energy, even with the tube(s) gone. A remedy is to replace the unnecessary tubes with dummy types, which draw little current but still provide a uniform lighting effect. This solution makes the most out of the energy used by the light fixture and also avoids the disturbing sight of a light with a gaping cavity hole where a lamp is missing. It also produces a more uniform light level on the work surface because the delicate photometrics of the fixture are not as skewed as if one lamp was completely burned out.
Reducing the light level for exterior or specialty lighting is much simpler: Just replace the lamp with a lower-wattage lamp, or a more efficient lamp or light source altogether.
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Excerpt from Energy Conservation Projects.