What Does A Grow Light Ballast Do? Why Are They Not Used In LED Grow Lights

I remember the first time I tried setting up indoor marijuana growing space; I was overwhelmed by the numerous factors to consider.

For instance, you have to think about the size of the grow tent, ventilation, and temperature.

But one thing that got me intrigued was the use of a ballast to operate a full spectrum lighting system for my cannabis growing system properly.

Basically, a ballast is your ultimate assurance that grow lights won’t blow up because it regulates the electrical arc within the grow light bulbs.

It also ensures your marijuana grow lights get enough voltage to get started.

To lengthen the life of your grow lights, you must maintain an optimum electrode temperature. Ballast can do this.

Once you have chosen your preferred grow light, the next step is knowing what kind of ballast you should choose and how it can help you with growing and reaping marijuana.

Takeaway: Using growing light ballast can reduce your energy consumption and maintenance costs by running different lights such as metal halide, mercury vapor, and HID lighting.

Below, we discuss the purpose of a grow light ballast. What does a ballast do? And why do LED grow lights not require a ballast like HID lighting?

What’s In A Ballast?

Each ballast has a particular power and must be in accordance with the bulb’s voltage.

Some ballasts have a regulator to modify the voltage, while others only have a single output voltage.

Ballasts run on either a 120V or a 240V power connection. Some commercial models can operate at 220V, 347V, 400V, and 480V.

Those with fixed voltage can be used in flowering spaces or mother plant rooms where the light is continuously operating.

Adjustable ballasts can be used in marijuana growing rooms where the whole growing cycle is carried out.

Typically, you can modify the setting to 50%, 75%, 100%, and 110% of the electrical current on most models.

Typically, cannabis growers use a 600W ballast.

Depending on the particular model, the ballast can be adjusted to 250W, 400W, 440W, or 660W.

In addition, at its lowest setting, a ballast can help root cuttings or sprout seeds grow better.

Ballasts set at 75% are optimal for growing marijuana, while a setting at 100% is suitable for flowering and finally at 110% is best for fattening buds.

Note that a ballast produces heat between 60 degrees Fahrenheit and 150 degrees Fahrenheit.

Fortunately, some models are fitted with small ventilation fans to cool the ballasts, making them more efficient in marijuana growing.

What Does A Grow Light Ballast Do?

Using Light Grow Ballast

A grow light ballast can control the current that is fed into the grow lamps.

They also ensure the correct voltage to power up the grow lamps.

Most importantly, grow lights draw power from a high-voltage source.

This may lead to high electrical current spikes.

Grow light ballasts control and limit the electrical current so that these surges or flashes of electricity don’t damage the grow light. 

Moreover, two mechanisms power up grow lights: an electrical arc and gas.

The bulb gets enough voltage to start that electrical arc to melt the solid into a gas.

However, once that solid turns to gas, the bulb doesn’t need much electricity to keep itself lit.

In the gaseous state, the lamp resistance plummets. Your light will then only need less power to keep operating.

Hence, a grow light ballast helps control how much electricity your bulb receives so it can operate the way it needs to.

If there’s no ballast, your bulb could either produce too much electricity or blow up.

Any traditional tube fluorescent bulb and high-intensity bulbs require a ballast.

High-Pressure Sodium (HPS), Metal Halide (MH), and Ceramic Metal Halide (CMH) bulbs all need a ballast.

When it comes to HID bulbs, you will need more power than your outlet can provide.

The ballast boosts power to give HID bulbs the necessary push to keep running.

Once lighted up, the ballast ensures HID bulbs constantly get an electricity supply. Here’s what it can typically cover:

  • 150W = 1-3 weed plants
  • 250W = 3-5 weed plants
  • 400W = 6-9 weed plants
  • 600W = 9-12 weed plants
  • 1000W = 12-16+ weed plants

Furthermore, HID bulbs require more power to run when they age. A ballast automatically surges the amount of energy for the bulb.

If a bulb reaches a point that requires too much power, the ballast will shut down to avoid any accident.

When you try turning the bulb on again, but the ballast deters it, this indicates that it’s wise to get a new bulb.

Ballast Size

Grow Light Ballast

Different ballasts mean different amounts of electrical energy that can be lost.

That amount depends on the size of a ballast’s coil and iron core.

The new international standard for ballast size has fallen to 30mm x 30mm or 1.18 inches for the cross-section.

Subsequently, ballasts became lighter and smaller.

Many models are now designed with universal voltage capacity, permitting input voltages from 100V to 300V.

There’s a chance for more energy to be lost when you have a bigger ballast size.

For instance, a 36-watt light will lose about 25% of energy despite having standard ballast.

What Happens When There’s No Ballast?

As I’ve explained earlier, fluorescent lamps give light to marijuana.

Yet, lamps need a ballast to help regulate the current and provide enough voltage to operate.

For instance, fluorescent ballasts are built for higher-wattage CFLs with 26W, 32W, or 42W power ratings.

However, it would still depend on your fluorescent bulb diameter size.

The two most efficient sizes are T5 and T8 bulbs, while the T12 bulbs are the least efficient.

A common way to estimate the system wattage of a CFL fixture is by multiplying the lamp wattage by the number of lamps and the ballast factor.

lamp wattage x number of lamps x ballast factor = estimated total system wattage.

So if you have a 32W bulb, the energy usage breakdown could be:

Light WattRange
32W bulb x 1 bulb x 0.78 (low ballast factor) = 29.96WRange from ballast catalogs: 25W to 26W
32W bulb x 1 bulb x 0.88 (normal ballast factor) = 28.16WRange from ballast catalogs: 28 to 31W
32W bulb x 1 bulb x 1.2 (high ballast factor) = 38.4WRange from ballast catalogs: 38W to 41W

As you can see, the ballast helps produce high voltage to get the electrical arc started.

When the arc strikes, the sodium is solid but rapidly melts and becomes gas.

If there’s no ballast to limit the current, a fluorescent lamp connected to a high-voltage power source would overwhelmingly intensify its current draw.

Choosing the Right Lighting Ballast For Growing

There are two main types of growing light ballasts for indoor marijuana growers: magnetic ballasts and electronic ballasts.

Experienced cannabis growers would have probably used old-school magnetic ballasts with transformer coils and a capacitor starter that regulate the voltage.

Many marijuana growers favor magnetic ballasts because of their low price, but they disperse heat energy.

Consequently, your growing area gets higher temperature and power consumption.

On the other hand, electronic ballasts are smaller yet more efficient tools to operate at low temperatures.

Moreover, electronic ballasts don’t emanate vibrations. They can also avoid the usual flickering, which is present in magnetic ballasts.

If you want a stable power flow and a lengthened lifetime of your bulbs, using electronic ballasts is a wise option.

Magnetic Ballast Vs Electronic Ballast

When there are advantages, there are also disadvantages.

Know that setbacks are not hindrances, but you must consider your cannabis growing conditions to know what works best for you.

A 1-lamp, 2ft T12 with magnetic ballast has a typical wattage of 28.

Meanwhile, a 1-lamp T8 with an electronic ballast has a typical wattage of 28.16.

Personally, I would go for electronic ballasts because of their efficiency.

​Electronic ballasts are cooler and produce a higher output while using less power.

Most electronic ballasts are dimmable, allowing them to run lower-wattage bulbs, MH bulbs, and HPS bulbs.

How Does A Magnetic Ballast Work?

A magnetic ballast has a large spool of wire wrapped around steel sheets.

This generator produces a large amount of voltage necessary to power up a bulb.

Magnetic ballasts usually last longer than electronic ballasts.

They can even operate for years in harsh conditions.

This is ideal if you want a model that can match the long-term needs of your marijuana.

Moreover, they are manufactured to meet the American National Standards Institute (ANSI) standards, which guarantee a ballast and a lamp run together correctly.

However, magnetic ballasts are bulky and release a lot of heat.

Similarly, MH and HPS bulbs have different requirements, including separate ballasts.

Nevertheless, switchable magnetic ballasts can run both types of bulbs, yet they are designed for HPS specifications.

Since magnetic ballasts are single-purpose, they are not interchangeable as well. For example, a 600W ballast must be used for a 600W bulb.

When using magnetic ballasts, lights that accumulate 39 to 175 watts of energy will lose between 14.6 and 37.6 watts of energy.

In addition, they consume 8 to 10 watts when operating with the lamp in the circuit.

The ballast will take about 4 watts when the lamps are removed, but the ballast remains energized.

How Does An Electronic Ballast Work?

Electronic ballasts use microchips and semiconductors instead of a magnetic coil to provide the high voltage needed by HID lamps.

The good news is that an electronic ballast provides up to 30% more light than magnetic ones despite having similar energy consumption.

Since there’s no heavy coil, electronic ballasts are lighter, smaller, and a lot cooler.

Unfortunately, there’s no ANSI standard for compatibility with the 250+ watts versions of MH and HPS lamps.

This is why we suggest purchasing a complete lighting package for growing marijuana.

As a result, you ensure the ballast was designed to operate the included light bulbs.

On the bright side, almost all electronic ballasts are switchable, which permits them to run both MH and HPS bulbs without issue.

Additionally, most electronic ballasts are dimmable, giving you the freedom to run multiple wattages of bulbs.

What Is A Digital Ballast?

Digital Ballast

In some cases, you’ll see electronic ballasts labeled as ‘digital ballasts.’ Yet, very few are digital.

This is when a ballast contains a microprocessor.

What’s good about a digital ballast is that it can execute the same functions as electronic ballasts but can deliver a higher level of precision in producing power.

Digital ballasts are also dimmable to any point between 400 to 1,000 watts.

As a result, you attain an appropriate amount of lighting for growing marijuana.

However, this is often the most expensive type since digital and electronic ballasts are not interchangeable.

Can I Use Ballast With A Ceramic-Based Bulb?

From what I’ve seen, ceramic-based lights are either 315W, 630W, or 945W.

These wattages could be complex in pairing up with a ballast that is not explicitly made for them.

Ceramic-based lights are outside standard grow light wattages, which makes it challenging to find the right ballast.

Generally, a dimmable ballast is best used in these settings:

  • 250W bulb = 300W ballast
  • 400W bulb = 500W ballast
  • 600W bulb = 750W ballast

For example, a 600W ballast may not be compatible with a 315W bulb.

But you’ll be fine as long as you are not under-or over-powering your bulb for marijuana growing.

Do LED Grow Lights Need A Ballast?

Ballasts power the light bulbs.

Fluorescent lamps have built-in ballast.

HID lights need to be paired with ballast to create an exceptionally high voltage to initiate an HID bulb’s electrical arc.

Meanwhile, LED lights don’t require a ballast because they can be plugged directly into a standard electrical socket.

LED lights don’t require a ballast. After all, they operate differently because they only need direct current.

When you use LED lights to grow cannabis, everything you need is included in the package, so an extra component, like a ballast, is unnecessary.

Where To Get A Light Ballast

As mentioned before, the easiest route is to buy yourself a complete lighting kit.

Kits usually come with a ballast, a metal halide bulb, a high-pressure sodium bulb, hangers, a reflector, and a timer.

A Word Of Caution

  • Magnetic ballasts can get hot because they are the main producers of heat when using HID lamps.
  • Keep the ballast outside your cannabis growing space to help control the temperature.
  • Ensure that magnetic ballasts are well-ventilated. Hence, they should never be covered.
  • Keep your ballasts clean because lint and dust can trigger fires.
  • Ballasts are high-voltage equipment, so always be careful to avoid electrocution.
  • Always unplug a ballast before handling it.
  • Secure cables to the walls or ceiling of your marijuana-growing space.

Choosing The Right Ballast

A ballast acts as a transformer to supply a light bulb with enough voltage to help the bulb jumpstart.

It will regulate voltage surge, so there’s less current when the bulb is warming up.

Ensure you’ve correctly matched the ballast’s wattage to the wattage rating of your bulb type to maximize the power of your tools.

When you have chosen the appropriate ballast for your grow lights, you boost the power of having a prosperous indoor soil and grow kit.


What does a grow light ballast do?

A grow light ballast controls the electric current that is delivered to the lights, hence ensuring that the correct voltage is used to power the grow lights. Ballasts are important because grow lights require a high voltage source to operate, so controlling the current is imperative.

Do I need a ballast for LED grow lights?

Modern LED grow lights do not require a ballast. However, there are some that are designed to work with an existing ballast. LED grow lights that are ballast-compatible or “plug-and-play” are available to replace various types of lights such as linear and compact fluorescents or HIDs.

What does a ballast do for HPS?

The purpose of a ballast is to regulate the current of power to the bulb in order for it to be safe and run efficiently. The current from a regular electric socket is too much for a HPS (High Pressure Sodium) bulb, and if a ballast was not used, the bulb would explode due to the overflow of electricity the bulb can handle.

Can a ballast catch fire?

Though a ballast cannot catch on fire directly—it’s main function is to control electric current—it can ignite nearby combustible objects like fluorescent bulbs. The gases in fluorescent bulbs are what will cause fires; ballasts could generate a spark that starts the fire.

How long does ballast last?

A standard ballast can last for more than ten years! However, with proper maintenance and environmental factors such as cold weather or faulty bulbs, the lifespan can be reduced.


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