Using More Grow Lights Efficiently and Safely

By Casey Jones Fraser
Published: November 1, 2013 | Last updated: August 8, 2022 07:19:40
Key Takeaways

Years ago, many indoor gardens had only one light in the flowering set-up. That is not the case today. In this article, Casey Jones Fraser explains how to power up all your lights without blowing a breaker.

Fifteen years ago, the big debate was whether or not to have a separate growroom for vegetative growth. These days, most growers know that a healthy vegetative garden is key to the flowering phase.


So, with the trend toward raising more and healthier vegetative plants in order to increase the flowering garden, the need for more lights has risen as well.

Growing with multiple lights gives options like perpetual (or, staggered) harvests, side-by-side comparisons and bigger production. However, while many growers would like to take advantage of these options, not everyone knows how to meet the electrical requirements involved.


Most growrooms in residential homes have one or two electrical circuits with 15 A per circuit. If you have two circuits, this limits you to two 1,000 W lights or four 600 W lights. If you only have one circuit, you can get away with a single 1,000 W light or two 600 W lights.

So, how do ambitious growers seeking numbers like four, six, or eight HID lights in a garden power these things without blowing breakers?

That’s where lighting control boxes come in to play. The boxes are like beefed-up power strips for grow lights. Running on 240-V power, lighting control boxes allow growers to plug in multiple lights on a single circuit.


These units have two power cords: one big one that powers the grow lights and a small “trigger cable” for connecting to a timer. The trigger cable does not power any equipment; it simply triggers the on/off switch for the control box. Some control boxes omit the trigger cable and incorporate a built-in timer instead.

Understanding Voltage and Grow Lights

The standard electrical outlets in your house operate on 120-V power. This is the voltage for powering toasters, televisions, computers, etc. Electric stoves, dryers and other high-powered appliances use 240-V outlets.


The ballasts that power HID grow lights can operate on 120 or 240 V, but they must be wired specifically for the matching voltage. Many electronic ballasts can be used on either voltage with no switching or rewiring. Still, always check the label on the ballast to avoid damage.

Higher voltage translates to lower amperage, and that allows for more lights. When ballasts are functioning with double the voltage, the amperage is cut in half.

For example, a 1,000 W HPS light uses 9.5 A when plugged into 120 V. When that same ballast is operating on 240 V, the amperage is 4.75. That means you can plug in another ballast without blowing a breaker.

With a 30-A circuit at 240 V, you could safely run up to five 1,000 W lights. Would you rather grow with two lights or five? Just think about the harvests!

Please note that this is not an electricity-savings technique. Grow lights use the same amount of electricity regardless of the voltage. Switching to 240 V will not reduce your power bill.

Grow Light Power Options

Go look at the cable on the back of your dryer. That is one big power cord. When you are dealing with 240 V, the large power capacity requires a large cable and outlet. One of the best ways to run a lighting control box is with a dryer cord. Many indoor gardens are set up near a laundry area so that dryer outlet is conveniently located nearby.

If your basement has a dryer outlet, visit a quality hydroponics store and ask for a lighting control box with the correct style of dryer cable to match your outlet. Mount the box and plug in the big power cord. The control box will have power outlets for the ballasts.

Make sure the ballasts are setup for 240 V and then plug them into the lighting control box. The final step is plugging the trigger cable into a regular 120-V timer. The lights are powered through the dryer cable, and the trigger cable turns the lights on/off.

With those four steps, you can run multiple lights with minimal effort. All of the lights are controlled by the single timer.

Stove outlets can run even more lights. While dryer outlets often have a 30-A circuit, electric ranges typically boast 50-A outlets. At 240 V, the larger amperage allows growers to use eight lights with plenty of headroom. Just picture eight ballasts plugged into one box and one timer.

If you are comfortable adding breakers to the electrical panel in your house, you can skip the outlet and simply hardwire your lighting control box. Simply run a length of solid-core cable directly from your breaker panel to your growroom and wire that cable to your control box. Note that you will still need to plug the trigger cable into a 120-V timer for on/off cycles.

You may be thinking, “I’d love to use my dryer outlet or stove outlet for grow lights, but I use my dryer and stove!” No problem. Qualified repairmen can tap into either of those outlets and run a cable from your kitchen into your growroom, where the lighting control box is positioned.

Your appliance stays plugged in, but the grow lights are wired to the same circuit. The important thing to remember, however, is to never run your appliance from that outlet while the grow lights are on. So, if your grow lights are on at night, do your laundry and cooking during the day.

If you need access to your appliances 24/7, your best option is to hard-wire the device to your breaker panel. This gives your grow lights a dedicated circuit, so no other devices can cause the breaker to trip.

While I am not a licensed electrician, I am able to safely and legally install such devices in my home with ease. If you have no experience with electrical repair, get a qualified installer to add a circuit for the garden.

So, don’t be afraid to run multiple grow lights. You will need plenty of fans, air conditioning and various growing supplies to go along with the lights, but the big harvests are always worth it. With lighting control boxes, adding more lights is a snap.

Check your local grow store to see these boxes up close, and ask about various power options for your garden.


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Written by Casey Jones Fraser

Profile Picture of Casey Jones Fraser
Casey Jones Fraser owns Garden Grove Organics in northern Kentucky/Greater Cincinnati. He has a degree in communications and electronic media. He believes that indoor gardeners can achieve the highest-quality crops and maximum yields when proper science is applied. Since 1998, Casey has been testing various nutrients and supplements in search of outstanding harvests.

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