Magnetic vs. Electronic Ballast: How to Choose One for Your Grow Lights

A ballast is the box that starts a grow lamp and then keeps the electrical current stable and limited so the bulb doesn't burn itself out. You need one for MH, HPS and LEC lamps, and you'll choose between two types: magnetic (cheap but hot, heavy and noisy) or electronic (pricier upfront, but cooler, lighter and more efficient). Plenty of the lamps used for indoor cannabis grows need one, so here's what a ballast is and how to pick the right one for your lighting.

First things first: what is a ballast? It's a piece of gear with one very important job: keeping a lamp's electrical current stable and capping it. You'll always need a separate ballast with MH (metal halide), HPS (high-pressure sodium) and LEC (light-emitting ceramic) lamps, while fluorescent tubes and CFL bulbs come with one built in.

Ballasts are a key part of any indoor cannabis lighting setup.

How the different types of ballasts work

Today there are two types of ballasts for indoor cannabis grows: magnetic and electronic. Both do the same basic job of keeping the current that reaches your grow lamp stable and limited. Here's how each one works.

Magnetic ballasts

Magnetic ballasts are the old-school way to manage the power in a lighting system. Once plugged in, the ballast runs the current through copper coils to regulate how much electricity reaches the lamp. The downside is that this process throws off a lot of heat, so you need solid cooling to keep your plants from cooking.

Before you go magnetic, keep in mind that these ballasts can waste a lot of energy as heat, and just a few of them can noticeably raise the temperature of your grow room.

Electronic ballasts

Electronic (or digital) ballasts are much more advanced devices that use semiconductors and electronic components to precisely regulate the voltage that reaches the bulb.

They usually have fins along the sides for air cooling, which helps keep the unit's temperature in check. To keep them running efficiently, it's important to set them up somewhere with good ventilation.

Benefits of electronic ballasts

• Energy efficiency: they run cooler than magnetic ballasts because they convert power instead of burning it off. In other words, more of the energy goes into lighting the bulb and less into making heat.
• Power control: many electronic ballasts include a built-in dimmer that lets you adjust the bulb's output. That gives you finer control over your lighting and can also help cut your power use.
• Polarity detection: electronic ballasts can identify the bulb's poles, which makes installing polarized equipment a lot simpler. No need to fuss when you put the bulb in: just plug it in and go.

Electronic vs. magnetic ballasts: which one should you buy?

When you're picking a ballast for your lighting setup, you need to understand the key differences between electronic and magnetic models. Both do the basic job of controlling the current, but they differ a lot in performance, efficiency and features.

• Cost and efficiency: Electronic ballasts can cost more upfront than magnetic ones. Still, their better energy efficiency can add up to real savings over time, more than paying back the price difference.
• Heat: Magnetic ballasts are known for running hotter than electronic ones, so you may need extra cooling to keep your grow environment in the sweet spot.
• Weight: Electronic ballasts are generally lighter than magnetic ones, which makes them easier to install and move around.
• Power control: electronic ballasts very often come with a dial that lets you adjust the light output. That gives you more control over your lighting conditions.
• Bulb life: Bulbs can last longer when run on electronic ballasts, which can cut your replacement costs.
• Restrike time: Magnetic ballasts can take longer to fire the lamp back up after a power outage.
• Power draw at startup: Magnetic ballasts can pull up to twice as much power at startup as electronic ones.
• Noise and vibration: Magnetic ballasts tend to hum and vibrate more than electronic ones.
• Type of current: Electronic ballasts convert the power and drive the lamp at high frequency, while magnetic ones simply pass along standard alternating current.

Recommended grow light ballasts

The Spiderlux Digital 600 W electronic ballast has a solid reputation as one of the best in its class. Built for 600 W bulbs with an E40 (mogul) base, it uses high-quality components and is rated at close to 100% efficiency.

It also keeps wasted energy to a minimum, so most of the power it draws goes into lighting your plants. And for all that efficiency, it gives off very little heat, which helps keep your grow environment dialed in.

On the magnetic side, our top pick is the SpiderLux Magnetic 600 W ballast, which has earned a reputation as one of the most efficient on the market. It's especially easy to use thanks to its plug-and-play connection, which makes installation a breeze, and it delivers excellent, consistent performance.

Whichever ballast you go with, think about your grow space, the kind of plants you're growing, your lights, whether you have ventilation and the other factors we covered above. Take a hard look at each one so your plants grow healthy and strong. At the end of the day, it's all about harvesting top-quality buds that are high in THC and taste amazing.