Linear Fluorescent Lamps

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Introduction

According to a recent study funded by the U.S. Department of Energy's Energy Efficiency and Renewable Energy Office (DOE EERE), lighting accounts for 22% of all electricity consumed in the United States. Commercial businesses consume 20% to 30% of their total energy just for lighting. And, 50% or more of that lighting-related energy may be wasted by obsolete equipment, inadequate maintenance or inefficient use. Upgrading lighting systems is one of the best energy efficiency investments available to a commercial facility. Since linear fluorescent light accounts for the majority of a commercial building's lighting energy use, improving the efficiency of these systems can save significant amounts of energy and money.

Technology Options

Improved phosphors in fluorescent tubes and improved electrical performance offered by electronic ballasts have dramatically boosted the energy efficiency of linear fluorescent lighting systems.

Fluorescent tubes are available in differing lengths, diameters and with differing light characteristics (e.g., color, CRI, lumen output). The tasks performed in your facility will determine the lighting levels required, and therefore the equipment you need.

To ensure the efficient lighting energy performance, the fluorescent tube must match the ballast (the device that modifies a building’s power for the fluorescent tube). Ballasts are available in magnetic or electronic models. The more-modern electronic ballast, matched with an efficient fluorescent tube, can reduce the energy cost as much as 50%. One of the most common ways to save significant energy is upgrading T12 lamps with magnetic ballasts, found in most buildings, to T8 lamps with electronic ballasts. Many manufacturers offer T8/electronic ballast combinations. (The designation T12 or T8 refers to the size of the lamp.)

Efficiency Benefits

Below is an example provided by the U.S. Department of Energy's Federal Energy Management Program (FEMP) illustrating the energy and cost savings of efficient fluorescent/ballast combinations. The best available lighting system saves 30% over the conventional system in the scenario of two lamps plus ballast. Even the lamp/ballast combination at the recommended level saves 25% of the lighting costs (in the same scenario). This is a tremendous energy saving opportunity found in many commercial settings.

Cost-Effectiveness Example
Performance Base Model Recommended Level Best Available
Lamp and Ballast Type T12, 34 watts, magnetic ballast T8, 32 watts, electronic ballast T8, 32 watts, electronic ballast
Rated Lamp Output — 2 Lamps 5300 lumens 5600 lumens 6000 lumens
Actual Light Output with Ballast (a) 4738 lumens 5018 lumens 5256 lumens
Input Power 82 Watts 62 Watts 57 Watts
Annual Energy Usage 295 kWh 223 kWh 205 kWh/td>
Annual Energy Cost $17.70 $13.40 $12.30
Annual Energy Cost Savings — 2 Lamps + Ballast - $4.30 $5.40
Annual Energy Cost — 2 Lamps Only - $1.30 $1.80
Lifetime Energy Cost Savings — per Lamp (b) - $2.80 $3.90
(a) Not including fixture performance, which affects total light output from the luminaire.
(b) Lifetime energy cost savings is the sum of the discounted value of annual energy cost savings based on average usage and an assumed lamp life of 5 years. Future energy price trends and a discount rate of 3.4% are based on federal guidelines (effective from April 2000 to March 2001).
Cost-Effectiveness Assumptions: Usage assumption is 3,600 operating hours/year. Assumed electricity price: $0.06/kWh, the Federal average electricity price in the United States.

Manufacturers

The following sources provide a list of manufacturers of linear fluorescent lights and ballasts.

Purchasing Tips

Upgrading lamps and ballasts together is recommended to achieve maximum energy savings. Consult a lighting professional to determine the best lighting equipment for your application.

Emerging Technology

T5 lamps are a practical, new generation of fluorescent tube technology for general lighting, but due to their unique size, length and luminance they are better for new than retrofit installations. T5 lamps come in metric lengths and the lamp holders are generally smaller and incompatible with T8 and T12 holders. T5 lamps are slightly more efficient than T8 lamps, but have substantially higher luminance compared to T8 lamps, which can cause glare problems in existing installations. T5 lamps are often used for indirect lighting or in shielding or lensing applications. New installations can be designed around the smaller size, unique length and luminance characteristics of T5 lamps.

Academia, industry and the federal government are all investing significant research funds into the development of higher-efficiency lighting products. Solid-state lighting, based on light-emitting diodes (LEDs) or organic light- emitting diodes (OLEDs), is a promising area receiving major investment. This technology has already established itself in traffic lights, indicator lighting, mobile phone displays, exit signs and other signage. Further development may lead to greatly increased efficiencies for general illumination like offices and homes. This new technology could not only save operating costs directly, but also improve the lighting quality and reduce cooling loads for buildings (since it produces less heat).