The Florida Solar Energy Center Logo
 
 
 
Home > Research > Photovoltaics > Virgin Islands Energy Office > Building Energy Audits > General Lighting Recommendations

Stylized Text: General Lighting Recommendations.

Lighting

Most existing lighting systems have low-risk, highly profitable energy savings upgrade potential. As outlined in the highly successful EPA Green Lights Program, the following strategies are recommended:


Tailor Lighting Levels:

Many older lighting designs are based on higher illuminance levels than recommended by the Illumination Engineering Society (IES). A typical office lighting system should have ambient lighting levels between 40 and 60 foot candles. In many cases this can be achieved with as little as 1 watt per square foot of lighting intensity with proper luminaire design, T8 fluorescent lamps and electronic ballasts. The use of task lighting can allow even lower ambient illuminance levels. There are a multitude of options for correcting lighting levels at an existing installation. Changing lamps, ballasts and louvers, adding reflectors, or implementing a maintenance program are the basic choices.

Several of the Technical Analysis Reports from Hill & Bell showed office space using over 2 times the lighting power intensity required from an updated system. Redesigning the system could cost-effectively reduce lighting by half or more and drop the air conditioning load as well.

Electronic Ballasts:

Upgrading to electronic ballasts is recommended not only for the efficiency gains but also for the lower maintenance, and higher quality light they produce. Electronic ballasts last 50% longer, eliminate flicker, offer dimming capabilities, have less humming noise and render colors better than magnetic ballasts. Further savings are achieved with electronic ballasts because they de-energizing failed lamps. And, unlike most magnetic ballasts, one electronic ballast can be used to drive up to 4 lamps.

Automatic Controls:

Reducing watts is the first approach to maximizing lighting efficiency, but automatic controls can also provide substantial savings. Occupancy sensors, timed switches and dimming capabilities will reduce burn-time and/or light output cutting energy consumption and - usually to a lesser extent - peak demand. While these technologies alone are not as cost effective as lamp and ballast upgrades, they increase payback periods only slightly when included in a comprehensive lighting upgrade package. If savings from occupancy sensors are in doubt, inexpensive light loggers that record actual lighting use can be installed to provide accurate savings estimates.

Lighting Maintenance:

All lighting systems experience a decrease in light output and efficiency over time from four factors:

· Lamp light output decreases (lamp lumen depreciation)
· Dirt accumulates on fixtures and room surfaces (dirt depreciation)
· Lamps burn out
· Luminaire surface depreciation

Over time, these factors can degrade a system's efficiency by up to 60 percent. Thus a properly designed system that maximizes energy savings and meets the lighting need on installation will eventually fail to perform properly without a solid maintenance program.

While most maintenance managers are hesitant to replace lamps that are still operating, group relamping and cleaning can be less expensive than sporadic spot maintenance. A group relamping program performed at 70% of the rated life saves on labor costs over spot relamping and offers an ideal opportunity to clean the fixture.

Exit Signs:

Exit sign upgrades offer the greatest savings per investment dollar with various options available to reduce the typical 40-watt fixture with 10, 5 or even 0 watts. The choices for retrofit and full replacement options include:

Typical Wattage
Life in Years

Retrofit

 
Light emitting diode (LED)
2
25+
Low-wattage incadescent assembly
8-18
10
Compact fluorescent
10
2
New Exit Sign
a
Light-emitting diode (LED)
2-5
25+
Electroluminescent
1
10
Tritium or self luminous
0
10-20
Compact fluorescent
10
2

With the longest life span of any option, LED fixtures offer the highest net present value (NPV) or net profit.