How to Buy an Energy-Efficient Fluorescent Ballast

Information about energy-efficient fluorescent ballasts in this section includes the following:

Efficiency Recommendation
Cost-Effectiveness Example
Where to Find

Also provided is a portable document format version of How to Buy an Energy-Efficient Fluorescent Ballast (PDF 69 KB, 2 pp). Download Adobe Reader.

Efficiency Recommendation^a
Lamp Type	# of Lamps	Recommended BEF^{a, b}	Best Available BEF
Four-Foot and U-Tube Lamps
T8,32 Watts	1	2.54 or higher	3.00
	2	1.44 or higher	1.54
	3	0.93 or higher	1.06
	4	0.73 or higher	0.79
T12,34 Watts	1	2.64 or higher	3.05
	2	1.41 or higher	1.53
	3	0.93 or higher	0.95
Eight-Foot Lamps
T8,59 Watts	2	0.80 or higher	0.81
T12,60 Watts	2	0.80 or higher	0.80

^a Ballast efficacy factor (BEF) is the ratio of the ballast factor (BF) to input watts; it measures the efficiency of the lamp/ballast system relative to others using the same type and number of lamps. ^b Ballast factor (BF), also called relative light output (RLO), is the ratio of the light output of a lamp(s) operated by a ballast, to the light output of the same lamp(s) operated by a reference ballast at rated current and voltage.

Cost-Effectiveness Example
Performance	Base Model	Recommended Level	Best Available
Ballast BEF	1.09	1.44	1.54
Rated Lamp Output 2 Lamps	5300 lumens	5600 lumens	6000 lumens
Actual Light Output Ballast + 2 Lamps^a	4740 lumens	5020 lumens	5260 lumens
Input Power	82 watts	62 watts	57 watts
Annual Energy Use	295 kWh	223 kWh	205 kWh
Annual Energy Cost	$17.70	$13.40	$12.30
Annual Energy Cost Savings Ballast + 2 Lamps	—	$4.30	$5.40
Annual Energy Cost Savings Ballast Only	—	$3.00	$3.60
Lifetime Energy Cost Savings^b Ballast	—	$31	$37

^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 ballast life of 15 years. Future electricity 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. Three sets of lamps would be used over the assumed ballast lifespan of 15 years. Assumed electricity price is $0.06/kWh, the Federal average electricity price in the U.S.

Energy use and performance of a fluorescent lamp ballast depends on the performance of the lamps and the fixture which, together with the ballast(s), make up a luminaire (see separate energy-efficiency recommendation for fluorescent tube lamps). This example shows the cost-effectiveness of efficient fluorescent ballasts used in combination with efficient lamps. The example also shows lifetime energy cost savings for the improved ballast, net of the savings from improved lamps. Each case evaluates energy use by a two-lamp ballast matched with appropriate lamps, selected to provide a similar level of light output.

The base model operates two 4-foot T12, 34 watt lamps, all at a base level of efficiency. The recommended level ballast operates two energy-efficient 4-foot T8, 32 watt lamps. The best available ballast operates two 4-foot T8, 32 watt lamps with the best available efficiency (see "How to Buy an Energy-Efficient Fluorescent Tube Lamp.")

Where to Find Energy-Efficient Fluorescent Ballasts

The Federal supply sources for energy-efficient fluorescent ballasts are the Defense Logistics Agency (DLA) and the General Services Administration (GSA). DLA sells fluorescent ballasts through its Energy Efficient Lighting catalog, available on its Web site. GSA offers them on Schedule 62-II, as well as through its on-line shopping network, GSA Advantage! Choose ballasts that meet the recommended levels.

When contracting or buying from a commercial source, specify or select a ballast BEF that meets the Efficiency Recommendation for that lamp type and number.

Buyer Tips

BEFs may not be indicated in manufacturers' literature, and must then be specified or requested. BEFs also can be calculated, by dividing Ballast Factor (BF) by input watts.

Only electronic ballasts meet the recommended efficiency levels. However, in rare applications where sensitivity to electromagnetic interference is a particular concern, magnetic ballasts may be preferred; several Federal agency guide specifications provide guidance on appropriate applications for magnetic ballasts.

The most efficient ballasts for four-foot T8, 32 watt lamps are "instant-start" ballasts, which may shorten lamp life in applications where lamps are turned on and off frequently; slightly less efficient "rapid-start" ballasts are preferable in these applications. Electronic dimming ballasts can be used to vary light levels.

Fluorescent lamp ballasts should have an RLO between 85% and 105% in most applications, to maximize light output, avoid reduced lamp life, and prevent unnecessary power consumption. Total harmonic distortion (THD)^a should be 20% or less, to reduce interference with electronic equipment. Current crest factor (CCF)^b should be 1.7 or less, to avoid reduced lamp life.

^a Total harmonic distortion (THD) measures the degree to which the current wave shape is distorted from a sinusoidal wave, expressed as a percentage.
^b Current Crest Factor (CCF) is the ratio of the peak lamp current to the root mean squared (rms), or average lamp current. CCF has a range of 1 and above.

For More Information

FEMP's Federal Lighting Guide (PDF 1.7 MB, 53 pp) provides helpful guidance on lighting projects.
Phone: (877) 337-3463. Download Adobe Reader.
American Council for an Energy-Efficient Economy (ACEEE) publishes the Guide to Energy-Efficient Commercial Equipment, which includes a chapter on lighting.
Phone: (202) 429-0063
The Lighting Research Center has valuable information covering various lighting systems.
Phone: (518) 276-8716
E SOURCE publishes Lighting Technology Atlas (available to member organizations).
Phone: (303) 440-8500
Lawrence Berkeley National Laboratory provided supporting analysis for this recommendation.
Phone: (202) 646-7950