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Covered Product Category: Suspended Fluorescent Luminaires

The Federal Energy Management Program (FEMP) provides acquisition guidance and Federal efficiency requirements for Suspended Fluorescent Luminaires. Federal laws and requirements mandate that agencies meet these efficiency requirements in all procurement and acquisition actions that are not specifically exempted by law.

Meeting Energy Efficiency Requirements for Suspended Fluorescent Luminaires

Federal purchases must meet or exceed the minimum requirements listed in Table 1.

Table 1: Efficiency Requirements (LERa) for Federal Purchases
Optical Element Distribution Patternb Lamp Type
 F32T8 (lm/W) F54T5HO (lm/W)
Lensed 1’ x 4’ Semi-indirect ≥ 86 ≥ 72
Indirect ≥ 60 ≥ 65
Louvered 1’ x 4’ Direct ≥ 57 ≥ 50
Semi-direct ≥ 61 ≥ 54
Direct-indirect ≥ 69 ≥ 59
Semi-indirect ≥ 87 ≥ 70
Indirect ≥ 70 ≥ 53
Other 1’ x 4’c Direct ≥ 64 ≥ 61
Semi-direct ≥ 64 ≥ 58
Direct-indirect ≥ 70 N/Ad
Semi-indirect ≥ 86 ≥ 71
Indirect ≥ 83 ≥ 72
a LER = Luminaire Efficacy Rating in lumens/Watt (lm/W).
b Suspended luminaires are designated into five categories that differ by the percentage of light emitted in a direction above the horizontal plane of the luminaire. These categories are direct (0%-10% upward component), semi-direct (10%-40% upward), direct-indirect (40%-60% upward), semi-indirect (60%-90% upward) and indirect (90%-100% upward).
c Other indicates a primary optical element other than a lens or louver, such as a perforated diffuser or a combination of optical elements (not including the reflector or housing).
d N/A indicates too few models in the dataset to propose an ER for this lamp type.

 

Defining the Covered Product

The efficiency requirements in Table 1 apply to suspended luminaires with linear fluorescent lamps used in commercial and institutional buildings. Product performance must be measured in accordance with NEMA LE 5, Procedure for Determining Luminaire Efficacy Ratings Fluorescent Luminaires, using IESNA LM-41, ANSI C82.2-2002 for fluorescent ballasts, and ANSI C78.81-2005 for fluorescent lamps.

Reducing Energy Costs: Save More Than $125 by Purchasing Products That Exceed FEMP-Designated Efficiency Requirements

FEMP calculated1 that a product meeting FEMP-designated efficiency requirements is cost effective if it is priced no more than $125 above the less-efficient alternative. The best available model saves the average user more $159 above the less efficient model. The complete cost effectiveness example and associated assumptions are provided in Table 2.

Table 2. Lifetime Savings for Efficient Fluorescent Suspended Luminaires
Performance Best Availablea FEMP-Designated Efficiency Levelb Less Efficientc
LER (Luminaire Efficacy Rating) 78 (lm/W) 62 (lm/W) 35 (lm/W)
Power Input 55.5 Watts 60.9 Watts 78 Watts
Luminaire Light Outputd 4321 lm 3786 lm 2751 lm
Annual Energy Use 200 kWh 219 kWh 281 kWh
Adjusted Annual Energy Usee,f 127 kWh 159 kWh 281 kWh
Adjusted Annual Energy Cost $11 $14 $25
Lifetime Adj. Energy Cost (15 years) $131 $164 $290
Lifetime Energy Cost Savings $159 $125 ======
a The efficiency of the Best Available models was obtained during FEMP’s market analysis and more efficient products may have been introduced to the market since this information was published.
b Federal purchases must be of products that meet or exceed FEMP-designated efficiency levels.
c Less Efficient represents low efficiency fluorescent suspended luminaires in this category.
d Luminaire light output = initial lamp lumens * number of lamps * ballast factor * luminaire efficiency.
e Annual adjusted energy use is adjusted by the ratio of the light output of the less efficient model to the light output of the FEMP-designated, or best available, model. Annual energy cost and lifetime energy cost are also adjusted accordingly.
f Assumes that for FEMP-designated or best available luminaires, fewer luminaires or fewer numbers of lamps per luminaire can be used to provide equivalent light output to those of the less efficient model.

 

Exceptions

Products meeting FEMP-designated efficiency requirements or ENERGY STAR performance specifications may not be life cycle cost effective in certain low-use applications, such as when a device is being purchased for backup purposes and will remain in off mode for most of its useful life. For most other average or high-use applications, purchasers will find that energy-efficient products have the lowest life cycle cost.

Complying with Contracting Requirements

Legislation and the Federal Acquisition Regulations (FAR) require Federal agencies to specify and buy ENERGY STAR-qualified products or, in categories not included in the ENERGY STAR program, products that meet or exceed FEMP-designated efficiency requirements. Agencies that follow requirements to buy efficient products can realize substantial operating cost savings and help prevent pollution. As the world's largest consumer, the Federal Government can help pull the entire U.S. market toward greater energy efficiency, while saving taxpayer dollars.

These requirements apply to all forms of procurement, including construction guide specifications and project specifications; renovation, repair, maintenance, and energy service contracts; lease agreements; acquisitions made using purchase cards; and solicitations for offers. Energy-efficiency requirements should be included in both the evaluation criteria of solicitations and the evaluations of solicitation responses.

Federal Acquisition Regulation (FAR) Part 23.206 requires Federal agencies to insert the clause at FAR section 52.223-15 in solicitations and contracts that deliver, acquire, furnish, or specify energy-consuming products. FEMP recommends that agencies incorporate efficiency requirements into both the technical specification and evaluation sections of solicitations. Agencies may claim an exception to these requirements through a written finding that no ENERGY STAR-qualified or FEMP-designated product is available to meet the functional requirements, or that no such product is life cycle cost effective for the specific application.

Design and Installation Tips: Special Considerations

Suspended linear fluorescent luminaires have been on the market since the late 1980s and have become increasingly common in the commercial sector—particularly in offices, schools, retail, conference rooms, lobbies and healthcare buildings. These luminaires address the need to provide some amount of ambient light in the space, in addition to light on the task. The absence of ambient lighting in a space, for example one with high computer usage requiring light on the task and glare control, can provide too much contrast between dark walls and ceiling and the brighter work area. Suspended luminaires with some uplight component can both illuminate the task area and provide some light on the walls and ceiling—sometimes avoiding the need to install additional luminaires for ambient lighting.

Suspended luminaires are available in several light distribution categories that vary by the percentage of their uplight component: direct (no uplight), semi-direct, direct-indirect, semi-indirect, and indirect (100% uplight). Luminaire are also categorized by their light diffusion (optical) elements, using either lenses, louvers, or combinations of these, and other optical elements. Buyers should first choose the optical element(s) and light-distribution categories that meet the design needs of their application. They may then compare efficacies within that optical element and light distribution category. Efficiency requirements have been set for the most common combinations of optical element and light distribution categories found on the current market.

Efficient design includes the provision of adequate lighting for the application and tasks, using the lighting levels recommended by the Illuminating Engineering Society of North America. Building code requirements, which may have limits to watts/square foot as well as prescriptive requirements, should be followed. Care should be taken not to over light a space. FEMP-designated or best available luminaires may reduce energy use and costs, as well as purchase and installation costs, in comparison to less-efficient luminaires. For example, fewer efficient luminaires with higher light output may be required to light a space or luminaires with fewer numbers of lamps may be used to provide equivalent light output to that of less-efficient models using more lamps.

Buying Energy-Efficient Suspended Fluorescent Luminaires

Buyers are advised to compare LERs only within each luminaire category and subcategory, rather than choosing a luminaire for its LER value alone. Luminaire size, luminaire type, optical element, and lamp type may be selected for a variety of reasons based on the application—including color temperature, color rendition, light output, light distribution, rated lifetime and cost.

LERs should be readily available in manufacturers' literature. If they are not, ask your supplier for LER values. If LER is not available, buyers may calculate LER using this formula:

LER = (Luminaire Efficiency x Total Rated Lamp Lumens x Ballast Factor) ÷ (Luminaire Watts Input)

Luminaire Efficiency (LE), Total Rated Lamp Lumens, Ballast Factor (BF), and Luminaire Watts Input (input watts) may typically be found in manufacturers' product specification sheets and photometric reports.

Target efficacy rating (TER) is another informative metric for comparing luminaire effectiveness in delivering light to the application target. While LER uses luminaire efficiency (LE, percentage of total lamp lumens that leaves the luminaire), TER uses energy effectiveness factor (EEF, the percentage of total lamp lumens that reaches the specified target area typical of the luminaire) in its calculation of luminaire efficacy. Since TER is available in some but not all manufacturer literature, this guidance relies on LER as its efficiency metric. Lear more about the TER standard.

The fluorescent luminaire market, for both suspended and non-suspended products, is continuously evolving. Luminaire optical elements have become more varied and more efficient. For the past several years, luminaires using T5HO lamps have proliferated, and a modest number of T5 models have emerged. The market for electronic ballasts driving T8 fluorescent lamps has continued to shift toward subsequently more-efficient generations of high-performance ballasts and lamps, which increases the efficacy of the luminaires where they are incorporated. The most recent additions to the suspended luminaire market are products using LED light sources. However, not many models using LEDs are yet available, so this product overview does not cover luminaires using them.

User Tips: Using Products More Efficiently

In addition to selecting the optimal fluorescent luminaire for the application, building operators should operate lighting only when needed. The use of lighting controls, such as occupancy sensors, task tuning, and dimming when daylight is present (where applicable), should be considered to facilitate further energy savings.

Fluorescent luminaires should be maintained to retain their light levels. This includes periodically cleaning reflectors and changing lamps at a certain point in their average lamp lives (i.e., group relamping) to prevent costly maintenance from individual replacement due to lamps failure. Higher-efficiency lamps may have higher lumen maintenance over time or the lamps may have longer service lives, allowing longer group relamping periods.

Finding More Information

Lawrence Berkeley National Laboratory provided supporting analysis for this product overview.

Updated January 2014

1 Based on the following assumptions: Assumes the fluorescent luminaire is a suspended 2-foot x 4-foot louvered semi-direct luminaire using two F32T8 lamps that is used an average of 3,600 hours per year for 15 years, which is typical for Federal facilities. Annual energy use is based on NEMA’s LE 5 calculation. The electricity rate is $0.09 per kWh, the average at U.S. Federal facilities. Future electricity price trends and a 3% discount rate are based on Federal guidelines (NISTIR 85-3273-26) and are from the Annual Supplement to NIST Handbook 135 and NBS Special Publication 709, Energy Price Indices and Discount Factors for Life Cycle Cost Analysis, 2011.