Your Complete Introduction to Lighting Ballasts

Need an introduction to lighting ballasts? Here's our complete overview on this topic, in hopes of helping you find the ballasts that best meet your lighting needs. Have we missed something in this guide? Make sure to leave a comment and let us know. We'll make updates to cover as much as we can.

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What is a Lighting Ballast?

Let's start with what ballasts are. Outside the lighting world, a ballast is any kind of heavy material placed low in a ship to improve its stability. In this article, any mention of a ballast is about a lighting ballast. Similar to a ship ballast, a lighting ballast provides stability to a light bulb, or lamp.

(Light bulbs are called "lamps" in the lighting industry; we may use the terms "bulb," "lamp," "light," and in some cases "tube" interchangeably to refer to the item you're lighting up with a ballast.)

A lighting ballast provides this stability by generating the voltage needed to start a lamp and then continues to regulate the flow or current of electricity during operation. This is because the lamp itself cannot regulate this electrical current and, without a ballast, would quickly be destroyed.
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What Lamp Types Use Ballasts?

Incandescent light bulbs -- including halogen lamps -- do NOT require ballasts. This is because the electricity flows through a filament that resists or effectively regulates the flow. This resistance is what causes the filament to "incandesce," or glow from the heat. Of course it requires a lot of heat to cause a bright enough glow to light up a room, and this is why incandescent bulbs are so inefficient. The vast majority of energy goes toward producing heat rather than light.

LED lights also do NOT need ballasts, but use a different kind of electrical regulator called a driver.

This leaves us with gas discharge lamps, including fluorescent, metal halide, high pressure sodium, low pressure sodium, and mercury vapor lamps. All of these require lighting ballasts. Without going into detail about how these lamps work, each is filled with gases that become excited and emit photons (which we perceive as light) when charged by electricity. Since they do not have a filament to resist or regulate this electricity, the ballast does this work.

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Types of Ballast Technology

There are two main types of ballast technology: electromagnetic (commonly just called “magnetic”) and electronic.

Magnetic ballasts are an older technology, and they're no longer manufactured for fluorescent lights (due to legislation), though they are for HID lamps like metal halides and high pressure sodium bulbs. The frequent hum and flickering of fluorescent lights in the past was due to magnetic ballasts modulating current at a lower cycle rate.

Magnetic ballasts for HID lamps include core and coil ballasts and F-can ballasts. Core and coil are extremely popular for their low cost, long life, and versatility, but they are also noisy; so for indoor applications -- especially in quiet environments -- you would typically want an F-can ballast or an upgrade to an electronic HID ballast. (See the video below.)

Electronic ballasts (for either fluorescent or HID lamps) are a newer technology, and they're replacing magnetic ballasts in many settings. They regulate energy more efficiently than magnetic ballasts and therefore run lights at a lower cost.

There are also some hybrid ballasts that use magnetic ballast components while being run by some electronics for increased efficiency.

Despite the fact that electronic ballasts are a newer, more efficient technology, magnetic ballasts still offer an important benefit: they work well in cold temperatures. Because of this, they continue being used for HID lamps, which are often used in outdoor settings to light parking lots, streets, construction sites, etc.

​Fluorescent Ballast Start Technologies

Fluorescent ballasts start lamps with different technologies than HID ballasts. Here are the three main starting methods for fluorescent ballasts. (You'll find much of this information in our video below as well.)

Rapid Start Ballasts
These are the least efficient fluorescent ballasts, but they are necessary in locations where lights are turned on and off frequently (like in bathrooms, kitchens, etc.) rather than turned on once for the day. This is because rather than sending a surge of energy into a lamp, a rapid start ballast "ramps up" the energy sent, and this is gentler on a lamp and helps to prolong its life.

Because rapid start ballasts are suitable for lights that are turned on and off many times in a day, this type of ballast is needed when using occupancy sensors, which are increasingly being used in places like bathrooms, stairwells, and even lesser used hallways or warehouse areas.

Programmed Rapid Start Ballasts
Sometimes just called "programmed start ballasts," these share the same characteristics of the rapid start ballasts described above, but they're even more advanced, as they heat up a lamp to a precise temperature before turning it on. This improves the life of a lamp. So even though these ballasts are more expensive than other rapid start ballasts, they can save you money with longer lamp life and lower maintenance costs in replacing lights.

Instant Start Ballasts
These are the most energy efficient ballasts and therefore can save you the most money on energy costs where lights are left on throughout the day. Unlike rapid start ballasts, though, instant start ballasts start up lights with a surge of energy that causes more stress on the bulb and shortens its life span. This isn't effectively much of a problem when you're just turning lights on once or twice a day, but you wouldn't use these ballasts in frequent on/off locations.

Because these ballasts shorten the life of a bulb or lamp, you cannot use these with occupancy sensors or you will void the warranty of the bulbs.
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​HID Ballast Start Technologies

In the case of fluorescent lamps, the type of ballast used doesn't depend on the lamp type, but on the use of that lamp as described above.

In the case of HID ballasts, however, they are chosen according to the type of HID lamp being used. The two primary lamp and ballast types are probe start (older technology) and pulse start. In the case of probe start lamp and ballast systems, the starting probe is located inside the lamp. With pulse start lamp and ballast systems, the starting probe is located inside the ballast.

While pulse start systems are generally newer and more efficient than probe start systems, you wouldn't upgrade to pulse start ballasts if you still had probe start lamps. You would only make the ballast upgrade when changing the lamps themselves over to pulse start as well.

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​Ballast Factor

There are two fluorescent ballast terms involving "factor," so it's easy to be confused on this point. There is "Ballast Factor," which has to do with wattage used and lumen output, or how much light a lamp produces. We'll explain that in this section. There is also "Power Factor," which has to do with efficiency, or how much energy is used by a lamp and ballast system. We'll explain that in the next section.

In simple terms, you may have a low (below 1.0), normal (1.0), or high (above 1.0) ballast factor. Think of those as settings on a dimmer switch. If the dimmer is set to low, you'll get less light from a lamp, even though it's capable of producing more. In a similar way, a low ballast factor provides you with fewer lumens from a lamp than it states on its packaging (and uses fewer watts). A normal ballast factor provides you with the lamp's stated lumens (using the stated wattage). And a high ballast factor actually pushes a lamp to produce more lumens with more wattage than you see on the packaging, though it shortens the lamp's life as well.

Why would you choose a ballast with low or high ballast factors? Imagine you're retrofitting an older building with lamps that provide more lumens than the original lamps did. If you were already getting plenty of light from the old system, you can run new lamps on a lower ballast factor, providing the same amount of light while saving money on energy.

In a new construction setting, you may want to minimize the number of fixtures used. Ballasts with a high ballast factor can help in this goal by driving more light from fewer fixtures.

Ballast factor typically runs between about .70 and 1.20, which means that a ballast can run a lamp on up to 30% less energy (and produce 30% less light); or up to 20% more energy with 20% greater lumen output. You should also note that a single ballast may have more than one ballast factor, depending on the lamps it is running.

As one source points out, lamps run on a low ballast factor should use a rapid start method to reduce the loss of lamp life. The source also suggests, "This is particularly relevant for 32-watt F32T8 lamps operated at high frequency."

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Power Factor

Fluorescent ballast "power factor" is different than "ballast factor." This is about how efficiently a ballast uses its power, and is listed as a number between zero and one. If, for instance, a ballast has a power factor of .98, then it uses incoming electricity with 98% efficiency, which means it will require slightly more wattage than stated on a lamp in order to run that lamp.

Magnetic ballasts typically have low ballast power factors (below 1.0), while many of today's electronic fluorescent ballasts have a higher power factor, efficiently using energy to light their lamps.

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System Wattage

While "ballast factor" and "power factor" relate to fluorescent ballasts and help you determine the wattage used by the lamp and ballast system, when it comes to HID technology (like metal halides), you can simply look at a spec sheet or catalog to find this "system wattage." This is also sometimes known as "input power" or "watts input." For instance, a 400 watt metal halide lamp, combined with its ballast, may take 458 watts to actually operate.

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Fulham Ballasts

We thought we should touch on Fulham ballasts because of their unique place in the market. Once upon a time you would need one very specific ballast for one very specific lamp. You didn't have ballasts that would run multiple lamp configurations, so if you were running many types of lamps, you'd need just as many ballasts to run them.

This made it especially challenging for service repairs, as an electrician couldn't possibly stock all ballasts for all potential jobs. This caused delays in repairs while ballasts were found and delivered. And remember, those were "pre-internet" days when ballasts couldn't so easily be found and shipped.

Fulham came along with a real game changer: ballasts that could be used with multiple lamps in multiple configurations. Suddenly, with just a handful of ballasts on hand, and electrician could immediately replace an old ballast with a Fulham ballast by just keeping about a dozen products on hand.

Since then, ballasts from other companies have become a little more versatile as well, but Fulham's ballasts -- while perhaps a little less efficient than the others -- remain the most versatile. Because of their ability to run multiple configurations, however, it's important to have wiring diagrams for Fulham ballast installations. You can find their wiring diagrams here.

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How Do You Choose a Ballast?

A lighting ballast is not a one-size-fits-all kind of tool. It needs to fit the electrical requirements of the lamp that it will run. When purchasing a ballast, you'll need to read the type of lamps it's designed for, how many lamps it operates, and the voltage the lamps will run on. Choosing the right ballast for a lamp will optimize the light output and life of the bulb.

When it comes to HID lamps, the process is a little simpler: just match the ballast ANSI code to lamp ANSI code. (See the image below.)

​If you're confused about this during a purchase from Lighting Supply, simply call our friendly experts at 877-231-2852 for help with your order. They can help you to choose the correct ballast. The easiest approach to replacing a ballast is to order by the part number on the ballast, but our team can also provide you with compatible ballast options from other brands when needed.
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How Do You Replace a Fluorescent Ballast?

The following information applies when replacing a fluorescent ballast with its exact match (manufacturer number). When replacing with a different type of ballast, the process may get more involved, such as following a wiring diagram. In this case or when you have questions, we recommend asking or hiring a qualified electrician.

If you have an exact match replacement ballast (and wire connectors), you're comfortable with basic electrical work, and you can safely reach the ballast that needs replacing, the process is fairly straightforward:

• Shut off the power from your circuit breaker. Make sure there is no electricity running to your work with a non-contact voltage tester or similar tool. This step is critical to your safety.
• Cut the wires running to the original / old ballast. Make the cut close enough to the old ballast that the wires from the new ballast will easily reach the old wires.
• Remove the old ballast and install the new one.
• Strip about 1/2" of wire insulation from the old wires (and the new ones if needed) and use wire connectors to connect wires with identical insulation colors. If needed, cut off excess length from the new wires ahead of time, but make sure they'll still easily reach and connect with the old wires.
• Turn the power back on.

Again, this process assumes that you have the right tools and parts (an exact ballast replacement and wire connectors), that you can safely reach the ballast you're replacing, and that you're comfortable doing this kind of work. When in doubt, hire a qualified electrician.

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We hope this provides you with a useful introduction to lighting ballasts and that you'll share this resource with others. If you think we've missed something or could make something clearer, please let us know in the comments below. We'll try to keep this updated so it remains a valuable tool.