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The Ultimate Guide to Grow Lights

The wonderful world of grow lights. It’s fun, it’s complicated and there’s a lot to understand.

For a beginner, understanding the different types of grow lights, their effects on your plants (never mind your energy bills), and how to get your crops to do what you want them to do can be pretty overwhelming.

Thankfully, it doesn’t have to be. And all those acronyms that appear to be out to get you will quickly become your second language; allowing you to manipulate your grow space to get the most beautiful and tasty plants you can.

To help those just starting out, or for those that want to brush up on their knowledge, we’ve created this ultimate guide to grow lights. Everything from terminology cheat sheets to light coverage calculators, and comparisons of different light types is included, with plenty of links to further content to help, too.

Why are grow lights so great? 

if you want to grow indoors, you’ll likely need a grow light.

There are some major benefits to using a grow light. They allow your plants to keep growing, even when the weather outside has other ideas.

Plants need sunlight to grow. And once bedtime hits, they have to stop growing for a few hours until the sun comes back out. With LED lights NZ, you can create an always sunny environment for your plants – so that they’ll continue to grow, and you can harvest them quicker.

The biggest benefit is flexibility. Grow lights really open the door to a world of horticultural adventures. Whether you want to grow pineapples in the Antarctic, or leafy greens in the desert, grow lights allow you to create the perfect environment for your plants, no matter where you are.

Another benefit would be that you can create an even distribution of light. In the garden, plants may be prone to shade for most of the day; meaning they’re not getting as much light as the sun is giving out. Grow lights on the other hand, can help to evenly distribute light across your full plant’s canopy.

However, just to complicate things, there are different types of grow light, all offering different benefits. Understanding what advantages each type of grow light has will allow you to choose the perfect kit for your space and plant type.

LED Light Spectrums For Plants 

Placing a desk lamp over your pineapple plant isn’t going to have quite the same effect as a proper grow light. And that’s because a desk lamp doesn’t incorporate the full spectrum of light that your plants need.
The light spectrum is the part of the electromagnetic spectrum that’s visible to the human eye. The light spectrum for plants also includes UV and infrared radiation. Every part of the spectrum has something to offer your plants, and can be used to manipulate or enhance your plant’s grow cycle.

Below is a brief look at how different light colors are used within your plant’s growth cycle.

Red light (600-700nm) 

The red-light spectrum can help to create tall plants with lots of branches. There’s lots of red-light output from the sunshine in the Summer, and it’s this density of red light that stops chlorophyll being broken down within the plant. With more chlorophyll, your plants stay greener and look fresher throughout the Spring and Summer. So, if you want beautiful blooming plants to stay green and healthy during the Winter, red grow lights can help.

Red light is what tells plants when it’s the right time to start flowering. Without it, plants would flower during all seasons without the ideal condition to help them stay healthy.

This all sounds great, so why wouldn’t you just use red grow lights?

As with all good things, there are downsides. Using only red light can lead to tall, but very spindly, thin plants. Sure, there may be a lot of branches, but they’ll be weaker so unable to hold as much fruit or flower.

The red-light spectrum will be included in any full spectrum grow light, and is better when combined with blue light.

Blue Light (400-500nm) 

The blue light spectrum is a high energy spectrum that’s particularly good for the flowering phase of the growth cycle. Your grow light should always incorporate blue light as it’s these wavelengths that trigger photosynthesis within the photons.

Blue light helps the plant to regulate the opening of stomata cells on the plant’s surface. These cells open like doors to allow your plants to take in the carbon dioxide they need, while removing the water they don’t need.

Tip: It’s best to use blue light alongside other wavelengths as too much can lead to a decrease in PPFD.

Green Light (500-600nm) 

Green light is typically seen as the least effective light for photosynthesis. Chlorophyll struggles to absorb green wavelengths, so up to 50% of the green light that reaches your plant will be reflected away from the plant. This reflection is what makes leaves look greener.

However, when the plant has taken in as much red and blue light as possible, green light can still be absorbed – sneaking its way into the lower canopy – ultimately adding a little boost to photosynthesis

processes. Green light therefore can be used to improve the efficiency of photosynthesis in your plants, and to ensure lower leaves get the light they need.

Like blue light, green wavelengths can also help with regulating stomata.


Unlike blue, green and red wavelengths, ultraviolet light isn’t within the visible spectrum of light, and is classed as a radiation. Although there’s plenty of information about how bad UV can be for us humans, there are a few benefits for plants. There are three types of UV – UVA, UVB, UVC – ranging from 100-400nm. UVC doesn’t travel through the ozone layer but A and B are part of everyday light.

UV light can trigger your plants to create a protective layer to prevent sun damage, which overall will benefit your yield. This protective layer can also fight against stress and disease within the grow space.

Some research suggests UV can help to improve the flowering, yield and taste of your plants, too.

It’s starting to sound pretty good, but of course, UV should be used with added precaution. Like us humans, too much can cause serious damage to your plants.

You can buy UVC wands to help with cleaning your grow space and keeping it sterile. It’s ideal for fighting off microorganisms but as it’s such a strong radiation, it’s recommended that you ensure your plants are completely removed from the space, and you’re fully covered before you use it.


The use of infrared light for plant growth is pretty new. Only recently has research shown that plants are able to use much more of the light spectrum than we first thought. Ranging from 700-850nm, IR is the last wavelength on the spectrum that’s used by plants.

And it has an interesting effect.

Infrared creates a ‘shade avoidance’ response which makes plants stretch or lean toward the closest source of light. This is a natural response to the shade and it’s what helps keep photosynthesis ticking along. Infrared can be used to increase height for plants, as the lower canopy will attempt to grow taller to reach the light. Tip: IR light can trigger a quicker flowering phase. Usually, plants use phytochromes to process light and determine the right time of year to flower. With IR, you can trick plants into flowering at any time of year.

Do plants need darkness to grow? 

We talk a lot about light, but do plants need any darkness to grow? The simple answer is yes.

Plants can be grouped into three types: long day, short day and day neutral plants.

Understanding what type of plant you’re growing will allow you to understand just how much light and darkness your plants need. This is called the critical photoperiod and can be manipulated to create different outcomes for your plants.

Different types of grow light 

There are three common types of grow light, all of which have their own pros and cons. Traditional types of grow light include CMH and HPS lights, which are both high intensity discharge lights (HID). And then there’s LED grow lights, which have quickly become the industry favorite.

HPS grow lights glow a red orange colour, while CMH shines blue. As mentioned above, red is ideal for the flowering phase of the growth cycle, and blue is particularly good for vegetation.

When using HID lighting, it’s best to look at the light intensity each bulb offers. It’s measured in lumens, and the higher lumens, the better your grow. However, it’s also worth remembering that more light intensity can often mean more power and higher energy bills.

When comparing HPS and CMH, the major difference is availability. There are a number of HPS grow lights available, ranging from 250w to 1000w. Meanwhile, there’s really only one type of CMH grow light on the market: 315w.

That said, a two-bulb reflector for the CMH can create a 630w light with a colour range that outperforms their HPS counterparts.

Even after you’ve got your head around CMH and HPS, these grow lights come in two forms: Single or double ended.

Double ended grow lights can work at higher temperatures which can increase efficiency within the grow space. We recommend double ended grow lights for fruit bearing trees or commercial growing. If you’re just growing a few plants within a grow tent, a single ended bulb will be just fine.

LED Grow lights vs HPS 

When it comes to choosing your grow light, most people get stuck between a HPS light and an LED grow light. Both have their pros and cons, with HPS lighting typically being better suited to commercial growing.

This is because they’re pretty cheap to set up and offer a great light intensity – ultimately leading to bigger and better yields. However, while set up might be less expensive, HPS grow lights require continuous investment as the bulbs only last around 12-18 months. And, as they’re more intense and use more power, you’ll need to invest in high quality cooling systems and ventilation to keep your grow space the optimum temperature.

So it becomes pretty costly.

LED grow lights on the other hand are a little more expensive to set up but can last much longer. They require much less cooling – ultimately saving you money – and are pretty energy efficient.

Commercial growers are starting to turn to LED lighting to replace their traditional HPS lighting. The yields are still as high but LEDs run with half the power.

Different types of LED grow lights 

There are three types of LED grow light to know about: Infrared, UV and full spectrum.

As mentioned above, infrared grow lights are a supplemental light that can boost photosynthetic efficiency. It can make your plants grow taller, leafier and even change the taste or aroma.

UV grow lights aren’t particularly popular, as they can cause a lot of damage. If you want to ensure your grow lights include UV, look for ‘UV diodes’ in their description.

Full spectrum for LED grow lights is the most popular, and we recommend these types of grow lights to just about everyone. Full spectrum lights give you a vast range of wavelengths including the full visible light spectrum, IR and UV. They shine a bright white and give your plants everything they need. Our full spectrum HELIOS X LED grow lights come with a dimmer switch so you can adjust the amount of light your plants receive at different phases of the growth cycle to emulate their natural habitat.

Once you’ve got your head around the different types of light, there are two set ups to choose from: Quantum board or COB (chip on board).

Quantum board LEDs have single diodes attached to a board in rows. COB LEDs use LED chips rather than diodes.

How much does it cost to run an LED grow light? 

When calculating the cost of a grow light, it isn’t always just the lighting that needs to be considered. You might need additional heating or cooling systems depending on the type of plant you’re growing, and the type of light you’re using.

All of this kit needs power, meaning growing indoors can hike up your energy bills pretty quickly.

LED grow lights are popular because they’re so much more energy efficient than their predecessors. Meaning it’s unlikely you’ll need additional cooling systems in place.

We find this equation the best way to calculate your costs:

Total kilowatts x cost per kilowatt hour x hours per day x 30 day

How are LED grow lights made? 

Understanding how LED grow lights are made is a little complicated. Not every LED can be used as a grow light. Within the bulbs, there’s both positive and negatively charged materials that slot together and release energy during the process. When the energy is released, it’s this that creates the light you see.

When talking about LED grow lights, there’s at least 10 LED chips with at least 1 watt of power being used by each chip.

How to choose an LED grow light

By now you’ve probably noticed that we love an LED grow light. They’re super-efficient, easy to use and work for small or commercial growing spaces. What’s not to love?

We almost always recommend LED grow lights to our customers, and offer only the best on the market on our site.

But not everyone is same...

There are a number of manufacturers that will knowingly overexaggerate their LED’s abilities. Some will focus on the wattage of the bulb which – as we mentioned above – doesn't always mean more power or efficiency when it comes to LED grow lights.

Others might combine just blue and red diodes into one light and call it ‘full spectrum’. But ultimately, you’ll end up needing supplemental lighting to ensure your plants have everything they need.

Some manufacturers will also boast about the coverage of their grow lights. But rather than being disappointed in the results, we recommend pushing your plants into the center of the growth space and lighting it accordingly. Otherwise, plants at the sides will suffer in the shadows (quite literally).


How to calculate LED grow light coverage 

When looking at coverage, the aim of the game is to give your plants as much light as possible at any given time. This can be done by measuring your plant’s canopy and buying a number of grow lights to cover the whole space, or, by ensuring your plants are directly underneath the light source and away from the sides of your grow area.

Unfortunately, traditional, non-LED grow lights are much easier for calculating coverage. With LEDs it’s a little trickier and by no means a one-size-fits-all solution. A general rule of thumb is Light output / Desired light intensity but this might need tweaking depending on your space and the type of plant.

That’s why we’ve created this nifty table of some of our most popular grow lights and their coverage instead.

How to install a grow light 

So you’re finally at the stage where you want to install your grow lights. How high do they need to be? Or low? How do you attach them to your grow tent? What if you’re not using a grow tent? The questions go on.

Luckily for you, we’ve made it as easy as possible to install your grow lights as all our fixtures come with adjustable hangers included.

In terms of height, there’s no one correct answer...

Commercial growers with large-scale projects will find that there’s very little difference between hanging grow lights lower or higher above the plants. For small-scale grows, we recommend getting in touch so we can help! With more information about the shape or size of your space, the equipment you’re using the types of plants you’re looking to grow, we’ll have a better chance of calculating the optimum height for you.

How to use a grow light 

You’ve chosen your grow light, set it up in the grow space and you’re ready to get a blooming. But how do you actually use a grow light to get the most out of your plants? It’s time to take all the info from above and put it into practice.

Grow lights are typically used for at least 12 hours a day – replicating the amount of daylight your plants would receive in their natural habitat. Short day plants might be different, so it’s worth researching the plant’s photoperiodism before you get started.

Now all that’s left to do is experiment. Researching lighting recipes will be your new favourite thing. There are different combinations of red, blue and other light spectrums that are ideal for vegetation, flowering and other phases of the growth cycle. And with so many hobbyist growers out there, you actually have to do very little experimentation yourself.

We’ve linked a bunch of information into the post to try to help you as much as you can on your journey to being the best grower, but you’re bound to have more questions. If you’re stuck, don’t hesitate to get in touch with us!