Ballasts are electrical devices that convert line current into the proper voltage, amperage, and waveform to operate fluorescent lamps. The mix of ballasts has been shifting steadily toward more-efficient equipment over the past 10 years. High-efficiency electronic ballasts represent over half of new ballast sales in the U.S., and that share will grow rapidly because magnetic ballasts are effectively banned for many linear fluorescent lamps beginning in 2005 (see Electronic ballasts).

What Are the Options?

There are two basic categories of full-size fluorescent ballasts: electronic and magnetic. Figure 1 shows both types.

Magnetic ballasts provide output power to the lamp at line frequency (60 cycles per second in North America and 50 cycles per second in many other regions of the world).

Electronic ballasts use semiconductor technology to convert incoming 60-cycle power to drive the lamps with high-frequency current of 20,000 cycles per second or more. Electronic ballasts are more efficient in a number of ways. Most notably, they waste less power internally than magnetic ballasts, saving 3 to 8 watts per ballast. Because of their higher frequency, they drive lamps about 10 percent more efficiently than 60-cycle magnetic ballasts do. And those electronic ballasts with dimming capability save energy in multiple ways. For example, lumen compensation eliminates the need to overlight spaces when lamps are new, and reducing electric light levels when daylight is available also results in savings.

Some well-publicized failures of certain early-generation electronic ballasts made users wary of the technology’s reliability. However, manufacturers have worked hard to dispel these concerns with a combination of improved design and higher-quality control standards in components and assembly. Today, electronic ballasts from established suppliers are just as reliable, if not more so, than magnetic ballasts.

In September 2000, the U.S. Department of Energy (DOE) issued regulations that effectively banned the use of new magnetic ballasts for the most common types of T12 fluorescent lamps. The regulations include ballasts that are manufactured on or after April 1, 2005, sold on or after July 1, 2005, or incorporated into a luminaire by a luminaire manufacture on or after April 1, 2006. Although the rules do not specifically ban magnetic ballasts, they establish minimum ballast efficacy factors (BEFs) that are hard to achieve with a magnetic ballast. The rules do not cover ballasts for T8 lamps, because market forces are driving the use of electronic ballasts for most T8 applications.

Top of Page

How to Make the Best Choice

Ballasts are often the most expensive first-cost component of a lighting retrofit. Fluorescent lamp ballasts typically cost between $5 and $50. However, ballasts for high-power lamps, such as T12/VHO (very high output) lamps and some dimming electronic ballasts, can cost considerably more. There are generally substantial discounts for the purchase of the large number of ballasts needed for new construction or renovation. Ballasts last for 40,000 to 100,000 hours and operate with an electrical efficiency of about 80 to 95 percent, consuming parasitic power of about one to a dozen watts.

Following are the best choices for ballasts:

Electronic (high-frequency) ballasts. Electronic ballasts are about 10 percent more efficient than conventional line-frequency magnetic ballasts. They eliminate flicker and hum and are extremely cost-effective. The most efficient ballasts are defined in terms of BEF (Table 1). There are a few locations where it is still best to use magnetic ballasts: in recording studios, near radio-frequency security systems (such as those in bookstores), and in other extremely sensitive electronic environments that may be disturbed by high-frequency emanations from electronic ballasts. Although the DOE ballast rule effectively eliminates most magnetic ballasts used with T12 lamps, magnetic ballasts should still be available for T8 lamps in these niche markets.

High-frequency electronic ballasts with T8 lamps are typically the most efficient solution with the lowest lifecycle cost. There are some situations, however, in which it makes sense to use magnetic ballasts. These include settings where the equipment will operate in extremely hot or cold conditions and locations where there is a lot of sensitive electronic equipment. Electronic ballasts have been known to interfere with book detection systems in libraries, inventory security systems in stores, recording studio equipment, and some electronic medical equipment. Because they operate at much lower frequency, magnetic ballasts do not cause such interference and may be a safer choice in such settings.

Instant-start ballasts. This is the most efficient type of ballast, but it yields the shortest lamp life in most applications. It is a good choice for lamps that burn six hours or more per start.

Programmed-start or programmed rapid-start ballasts. Programmed-start ballasts, also known as programmed rapid-start ballasts, are improved versions on the older rapid-start technology that maximizes lamp life in almost all cases—although there is some penalty in efficiency. They are the best choice in applications where lights will frequently be turned on and off.

Universal-input ballasts. These ballasts typically accept any input voltage between 120 and 277 volts. They make retrofitting easier and reduce stocking requirements, but they are slightly less efficient than dedicated-voltage ballasts.

Dimming ballasts where appropriate. Fully dimmable fluorescent ballasts enable strategies such as automatic daylight dimming, lumen maintenance (automatically adjusting ballast power to compensate for the gradual loss of light output that all fluorescent lamps experience), occupancy-controlled and -scheduled dimming, and manual task dimming (whereby the occupant uses a rotary or sliding dimmer switch or PC control). Several dozen models of continuously dimming ballasts for full-size fluorescent lamps are now available in the U.S. market, and prices are dropping into the low-$30 range for two-lamp dimming ballasts.

Finally, check with manufacturers to make sure that lamps and ballasts are compatible. Most lamps are only compatible with one starting method; the exceptions are high-performance T8s, which can be rapid- or instant-started, and some rapid-start lamps that can be preheat-started.

Top of Page

What’s on the Horizon?

Wireless technology is playing an expanding role in a range of applications—including cell phones, computer peripherals, and Internet connections—and wireless lighting controls are not far behind. Wireless controls for limited niches such as conference rooms and classrooms, have been available for a number of years, but they are expensive and are sold based on the amenities that they provide. Newer systems that are more widely applicable and provide energy savings and load-shedding capabilities are in the works. Look for the first major products to appear in 2006.

Top of Page

Lighting designers have long been awaiting the emergence of low-cost, reliable, high-performance dimming electronic ballasts. That wish is closer to being realized, as several dozen models are now available and prices are dropping into the low $30 range for two-lamp dimming ballasts. Dimming ballasts can enable such strategies as automatic daylight dimming, lumen maintenance (automatically adjusting ballast power to compensate for the gradual loss of light output as fluorescent lamps age), occupancy-controlled and -scheduled dimming, and manual task dimming that gives occupants precise control over the light levels in their area. Dimming ballasts can also enable lighting loads to be minimized during periods of high electricity prices or to help facilities minimize demand charges.

Top of Page

Who Are the Manufacturers?