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A few years ago, installing fluorescent lighting meant contacting your dealer and asking for an electronic ballast and some lamps.
As technology has evolved, prices have come down along with energy use and maintenance needs, vastly increasing your viable alternatives and lowering your energy bills and operations headaches.
New lighting technology offers better light and easier maintenance, and in many cases, short paybacks even if you’ve previously performed a lighting upgrade.
But it also can mean a lot of confusion. We’ll help you make sense of it all by briefly explaining today’s options, where they work well and why you might consider them.
Choosing a lamp ...........................................................................
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Commodity-T8 ...............................................................................
6
Low-wattage T8 ..............................................................................
7
Super-T8 .........................................................................................
8
T5 ..................................................................................................
12
High-bay .......................................................................................
14
Indirect lighting ............................................................................
15
Choosing a ballast ......................................................................
16
Switch and save ..........................................................................
18
Beyond the bulb ..........................................................................
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Lighting consumes a tremendous amount of energy and financial resources.
Lighting accounts for approximately 17 percent of all electricity sold in the
United States.
ENERGY STAR ® estimates that if efficient lighting were used in all locations where it has been shown to be profitable throughout the country, the nation’s demand for electricity would be cut by more than 10 percent. This could save nearly $17 billion on electricity bills and result in the following annual pollution reductions:
• 202 million metric tons of carbon dioxide, which many scientists believe is the primary cause of global climate change. This would be the equivalent of taking
15 million cars off the road.
• More than 1.3 million metric tons of sulfur dioxide, which contributes to acid rain.
• 600,000 metric tons of nitrogen oxides, which contribute to smog.
(Source: www.energystar.gov)
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Fluorescent lights are commonly used for general area lighting, on ceilings and walls, and for perimeter areas. Because energy accounts for nearly
90 percent of the cost of owning and operating a fluorescent lighting system, choosing a high-efficiency product can reduce lighting bills significantly.
Therefore, it generally pays to buy the most efficient bulb available despite a higher purchase cost.
(Source: E Source)
Fluorescent options at a glance
Watts
Commodity-T8 Low-wattage T8 Super-T8
32
Lumens 2,700 to 3,200
25 to 30
2,400 to 2,900
32
3,100+
Efficacy (lumens/watt)
Rated average life (hours)
CRI
92 to 100
20,000
75 to 85
89 to 92
18,000 to 30,000
82 to 86
88+ / 90+ *
24,000+
81+
*Programmed rapid start ballasts/instant start ballasts
T5
28
2,900
104
20,000
82 to 85
T5HO
54
4,400 to 5,000
93
20,000
82 to 85

Lumen : measure of a lamp’s output of light
Efficacy : The light output of a lamp divided by the input power, expressed as lumens per watt (lm/W)
Color rendering index (CRI) : Measured on a scale of 0 to 100,
CRI describes the ability of a light source to render a sample of eight standard colors relative to a reference source
The intent of CRI is to describe how well the light source portrays colored objects compared to natural light. A CRI of 100 means that the source renders the eight standard colors in exactly the same way that the reference light source renders them. A lower CRI value indicates that some colors may appear unnatural when illuminated by the lamp.
Incandescent lamps have a CRI above 95. A CRI of 80 or greater is considered by the industry to provide excellent color rendering.
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Since more than 70 percent of the straight fluorescent lamps installed in businesses today are some form of T8 lamp, these have become the standard for energy-efficient linear fluorescent tubes. Most in use today are 32-watt lamps.
Good for:
• General lighting in commercial, institutional and industrial spaces with low to medium ceiling height
Pros
• Low cost
• High availability
Cons
• Higher energy use than some other fluorescent options
• Lower rated average life than some other fluorescent options
Lighting manufacturers have been improving T8 fluorescent lamps for many years by enhancing key performance characteristics, including light output, efficacy, rated life, maintained light output, and color, allowing for more flexibility in design of your lighting system.

Low-wattage lamps offer an energy-saving alternative to the standard T8 lamp.
Anything lower than 32W/bulb is considered low-wattage, however 28W and 25W bulbs are the most common lamp wattages.
Good for:
• Slightly overlit facilities since lower wattage means lower light output
Pros
• It’s a simple change from standard T8 lamps to the low-wattage lamps, so it’s a quick and easy way to save on energy bills
• Fast payback from energy savings if you’re changing out lamps upon burnout
Cons
• Not recommended where ambient temperatures fall below
60 degrees Fahrenheit
• Not recommended for use with low ballast factor, rapid-start or dimming ballasts, or with occupancy sensors
• Shorter lamp life in some situations
• Cost about two to three times as much as standard T8 lamps
(about the same as super T8 lamps). However, energy savings can quickly outweigh the additional cost
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High performance fluorescent T8 lamps, known as super-T8s, are more efficient, last longer and provide better color rendering than commodity T8s.
Their higher efficiency and longer lamp life provide a lifetime savings that often can justify their higher purchase price. In addition, their improved light quality often reduces the amount of lamps needed to produce necessary light, allowing you to delamp for further energy savings.
Super-T8s primarily use rare earth (RE) phosphors instead of the less- costly halophosphors typically used in commodity-T8s. RE phosphors convert ultraviolet energy to light more efficiently, provide higher lumen maintenance, and offer superior color rendering.
Super-T8s should be thought of as a system (lamp + ballast). Even though super-T8 lamps can be used with conventional electronic ballasts and super-
T8 ballasts can be used with conventional T8 lamps, the highest efficiencies are realized by using super-T8 lamps and ballasts together.

Good for:
• Spaces that are currently over lit since you can use a super-T8 and remove one or more lamps from the fixtures
• New construction or major retrofits since new ballasts and lamps are necessary for maximum energy savings
Pros
• Offers excellent color rendering (82 or higher)
• Delivers 10 percent more light than standard-T8s using the same energy
• Lasts 20 percent longer than standard-T8s
• Provides higher efficacy than standard-T8s
• Allows for increased design flexibility when fine-tuned with a variety of ballast factors
• Operates in rapid-start, programmed rapid-start, instant-start or dimming modes
Cons
• Super-T8 lamp/ballast system generally costs more than comparable standard-T8 system (although the paybacks and lifetime savings often outweigh the higher cost)
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What are Super-T8s?
Super-T8 technology is available for 2-, 3-, 4-, and 8-foot lamps, as well as for U-bent lamps. Xcel Energy uses the super-T8 specifications defined by the Consortium for Energy Efficiency. For example, a super-T8 fixture with
32-watt 4-foot lamps has the following requirements:
Lamps
• Produce 3,100 or more initial lumens
• Achieve 94 percent or higher lumen maintenance
• Provide mean lumens per watt of 90 or higher for instant start ballasts or 88 or higher for programmed rapid start ballasts
• Have a color rendering index (CRI) of 81 or higher
• Are rated for 24,000 hours or more (at 3 hours per start)
Ballasts
• Have a ballast efficacy factor (BEF) at least as high as the factors listed in the tables on the right
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Because of the variety of products on the market, before purchasing super-T8s, be sure to consult the Xcel Energy Lighting Efficiency rebate application to make sure the lamp and ballast combination qualifies for a rebate.
Or check with your Xcel Energy account manager or our Business Solutions Center at 1-800-481-4700 prior to ordering.
Lamps
Low
(BF<=0.85)
Normal
(0.85<BF<=1.0)
3
4
1
2
3.08
1.60
1.04
.79
3.11
1.58
1.05
.80
High
(BF=>1.01)
N/A
1.55
1.04
.77
Lamps
Low
(BF<=0.85)
Normal
(0.85<BF<=1.0)
High
(BF=>1.01)
3
4
1
2
2.84
1.48
.97
.76
2.84
1.47
1.00
.75
N/A
N/A
N/A
N/A
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To the casual observer, if smaller is better (T12s versus T8s), then T5s must be best.
This was actually true until the super-T8 came along. Even now, the standard T5 comes close enough in efficacy that it warrants serious consideration.
T5 lamps are available in standard output and high output (HO). The light output of a standard-T5 lamp is almost identical to a standard-T8 lamp, but uses a lower amount of energy. HO versions put out almost twice as much light as a T8 lamp of the similar length, and can therefore, cut in half the number of fixtures required in a given space or enable you to replace three-lamp T8 fixtures with two-lamp T5HO fixtures.
T5s work best with fixtures that limit glare since T5s emit more intense light than T8s.
In areas where glare is a problem, such as where computer monitors are in use, consider using indirect lighting.

Good for
• New construction or major renovations since T5 systems require a change of lamps, ballasts and fixtures
• Areas with space limitations since smaller fixtures are possible
Pros
• Smaller diameter permits downsized fixtures that can be placed farther apart and closer to the ceiling than with T8 lamps
• Reduced fixture light loss
• CRIs in the 80s
• More energy efficient than commodity-T8
• Higher optimal operating temperature allows T5s to perform better than T8s in enclosed fixtures and warm spaces
• Less manufacturing materials, including the phosphors that line the tube
• Less mercury and glass than T8 lamps, making them easier to recycle at end of life
Cons
• Available only in metric lengths (slightly shorter than T8s), so they use different sockets and ballasts than T8 or super-T8 systems
• More intense light produces glare in some situations
• Currently more expensive than T8 lamps (this should change as the technology evolves)
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High-intensity discharge (HID) light sources such as metal halide and high-pressure sodium lamps have long dominated the market for lighting indoor spaces with high ceilings. In recent years, advancements in fluorescent technologies have made fluorescent lighting (T8 or T5 lighting systems) the most cost-effective choice for lighting high indoor spaces.
Good for:
• Factories
• Warehouses
• Athletic facilities
• Large retail stores
Pros:
• Better energy efficiency
• Lower lumen depreciation rates
• Better dimming and occupancy- sensor options
• Virtually instant startup and restrike
• Better color rendition
• Reduced glare
Cons:
• Requires different fixtures than previous high-bay options (although some options use existing wiring)
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Indirect lighting, which typically features fixtures suspended from the ceiling that distribute light upward, is often combined with a certain amount of direct and/or task lighting.
Indirect lighting minimizes glare on computer screens and creates a soft, inviting environment. It can also be more energy efficient than direct lighting, because lower overall lighting levels are needed to provide the same light levels at work surfaces.
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Fluorescent lighting systems include both lamps and ballasts, so it’s important to consider the ballast, along with the lamps, when making a lighting change.
The ballast starts the lamps by providing the initial high voltage to strike an arc between electrodes and regulate the light output by maintaining a normal operating current and voltage.
Ballast starting mode
Lamps must be compatible with the starting mode of the ballast. In order to determine the overall system efficacy, you need to evaluate the lamp and ballast combination you choose. Ballasts are commonly available with two starting modes: instant-start and rapid-start.
Instant-start ballasts
Instant start ballasts are the most efficient and allow the lamps to start instantly, but can shorten the lamp life in situations where the lamps are turned on and off frequently.
Rapid-start ballasts
The newest rapid-start ballast is the programmed rapid-start ballast, which almost always lengthens lamp life but somewhat lowers efficiency.
Programmed rapid-start ballasts are best when lights will be frequently turned on and off. They’re appropriate for use with occupancy sensors, dimmers and controls, which will more than offset the loss in ballast efficiency.

Ballast factor
Ballast Factor (BF) is the ratio of lamp output when operated on a particular ballast to the rated lamp output. Values may range from roughly 0.7 to 1.2, allowing you to fine-tune your system by choosing a ballast with the desired ballast factor.
Ballast Efficacy Factor (BEF ) is the measurement used to compare the efficiency of different lighting systems. It’s figured as the ratio of ballast factor to the ballast supply power times 100.
(BEF = BF x 100 / input Watts)
Your lighting contractor will help evaluate these calculations and choose the best ballast for your lighting and efficiency needs.
(Note: Super-T8 rebates from Xcel Energy require specific ballasts. Check with your lighting contractor or our Lighting Efficiency rebate application form to ensure you choose a ballast that qualifies your lighting for a rebate.)
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If your facility still has T12 lamps, switching to T8 bulbs and electronic ballasts can cut 35 percent off your lighting bill compared to T12s.*
For even greater savings, switch from T12 or T8 to more-efficient options like super T8s, low-wattage T8s or T5s.
* (Source: E Source)
Adding specular reflectors (specially shaped metal sheets for ceiling-mounted fluorescent downlight fixtures that reflect light in a direct rather than a diffuse way), new lenses (thin plastic sheets covering recessed fluorescent fixtures at the ceiling level), and occupancy sensors or timers can double the savings.
Paybacks of one to three years are common.
Dimmable ballasts can provide control of the local lighting environment and cut energy use when they are adjusted relative to the available sunlight.
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This piece should give you a basic understanding of your fluorescent options.
Your next step is to talk to your lighting contractor about your specific application and available lighting solutions, or call Xcel Energy to learn about lighting solutions that qualify for our rebates.
As you consider your lighting options, it may be appropriate to install some sample fixtures to make sure the technology you choose will meet your needs.
Xcel Energy Lighting Efficiency rebates
Lighting Efficiency, by ConservationWise from Xcel Energy SM , offers rebates for
Minnesota and Colorado business customers installing qualifying energy-efficient lighting equipment, who receive their electricity from Xcel Energy.
“
We’ll help you find the solution that best fits your facility and your budget.
Start planning your energy savings today. Call 1-800-481-4700 , e-mail bsc@xcelenergy.com
or visit xcelenergy.com
and search for
Lighting Efficiency” to learn more about this and our other conservation rebate programs.
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Earn Lighting Efficiency rebates for fluorescent and other lighting technologies. Contact your Xcel Energy account manager or our
Business Solutions Center at 1-800-481-4700 for details.
References
Xcel Energy would like to thank the following resources:
E Source, ENERGY STAR ® and the U.S. Department of Energy, the Consortium for Energy Efficiency, and the Lighting Research Center
414 Nicollet Mall
Minneapolis, MN 55401
800-481-4700 xcelenergy.com
© 2007 Xcel Energy Inc.
Xcel Energy is a registered trademark of Xcel Energy Inc.
Northern States Power Company - Minnesota; Northern States Power Company - Wisconsin;
Public Service Company of Colorado; and Southwestern Public Service Company d/b/a Xcel Energy
07-08-226 | 09/2007 | CRS #1872
Printed with soy-based inks on recycled paper.