Before you start reading this guide, open up another tab in your browser and search the term “grow light.” Tons of results, right? And were they helpful? Probably not. That’s the problem: There are thousands of grow lights out there and not one place explaining exactly what you need to know to choose the best one.
That’s where this guide comes in handy.
In this guide, we’ll be focusing on the tried-and-true indoor grow lights that started it all: HID (high intensity discharge) grow lights. By the end, you’ll have all the tools necessary to choose the best grow light that suits your needs.
Whether you’re growing vegetables, fruit-bearing plants, or medicinal plants like cannabis, we’ll show you how to find the right grow light for you and your plants.
- Light bulbs
- How to Choose the Right HID Grow Light
- What the Experts Grow With
- Frequently Asked Questions (FAQs)
Before we get into the technical aspects of grow lights like watts and coverage areas, the best place to start is with the basics.
First, what the heck is a grow light?
Simply put, a grow light is a light that’s capable of growing plants. Technically, all lights can be grow lights, from the light bulbs in a desk lamp to the glow of a neon sign. However, if the light that’s given off from that source isn’t strong, plants don’t stand a chance of growing.
That’s what makes a grow light different than any other source of light: its strength. What separates one type of grow light from another is the way that it gives your plants light. For example, HID grow lights give you light through a chemical reaction, whereas LED grow lights give your plants light digitally. That said, what makes all grow lights the same is that they do one job and do it well: they grow plants.
Okay, but you can use the sun to grow plants. Why would I want to use a grow light to grow plants?
If your plants don’t get enough of the light they need, they’re going to have a hard time growing. You can’t guarantee that sunlight will provide everything your plants need to perform photosynthesis — the key to plant growth. There are two main reasons that illustrate why:
- Inaccessible Light: You may not be able to grow your own plants on rented property, and there are plenty of houses and apartments with yards that block out the sun for the majority of the day. Depending on where you live, you may not have a place where your plants can get adequate sunlight.
- Seasonal Growth: You may not be able to grow the specific plants you want year-round. Each season brings different amounts of light and wavelengths. That light controls how and when plants grow and harvest, and in nature, seasonal light only comes around once a year. With a grow light, you have the power to control that very same light and give it to your plants all year long.
Got it. Now how would I set one of these grow lights up?
Setting up a grow light is an incredibly easy task. Even with the most complex kit, there are really only five easy steps to setting up a grow light.
- Assemble the grow light reflector (if assembly is required).
- Install the bulb into the reflector.
- Plug your reflector and bulb into the ballast.
- Hang your grow light reflector/bulb.
- Plug your ballast into an electrical outlet and turn the ballast on.
It’s that simple.
Depending on where you want to grow — in a grow tent, closet, basement, or warehouse — you may have to think creatively when it comes to hanging and placing your grow light. Still, no matter what the configuration, the process is usually the same.
You’re going to see a lot of technical jargon out there when you’re looking for the perfect HID grow light. Some of it’s useful, some of it’s just fluff, and there’s a whole lot more people won’t tell you just to make a sale.
Before we get into the specifics of grow light equipment, it’s important we go over the science of it all. We’ll focus on the key attributes you should be looking at when you’re shopping for a new HID grow light and explain what they mean for your garden.
- Wattage: The wattage of a grow light refers to the amount of energy it will pull when it’s running. This is one of the very first things you’re going to see when shopping for a grow light. It’s also a good indicator of the amount of light the system will give your plants and the amount of heat it will produce. All in all, it’s helpful for getting an idea of its effectiveness on plants and how much it’s going to cost to grow yourself.
- Wavelength: Light runs along a spectrum of wavelengths (measured in nanometers, or “nm”), and only certain wavelengths of light are beneficial to plant growth. Some wavelengths will trigger plants to grow branches and foliage, while others stimulate flower and bud growth. If you buy the wrong light bulbs, your plants won’t be able to grow properly, so pay attention to the wavelengths your lights provide.
- Ultraviolet, or UV (200-380nm): All HID grow lights give off a small amount of UV wavelengths that help resin production and plant strength.
- Violet (380-445nm): This is mostly found in MH (metal halide) bulbs in very small amounts and helps the early stages of chlorophyl production, as well as leaf and stem growth.
- Blue (450-495nm): This is the key spectrum used in MH bulbs during the vegging stage of growth, responsible for foliar and branch growth.
- Green/Yellow (500-600nm): This is found in small amounts in all bulbs, and is absorbed in small amounts to be released when plants can’t get the other wavelengths (blue and red) they need.
- Red (630-660nm): This is the main spectrum used in HPS (high pressure sodium) bulbs during the flowering stage of growth. Specifically, it triggers plant cells to stop producing the majority of leaves and start producing flowers.
- Far Red (720-740nm, infrared, or IR): This is found in small amounts in HPS bulbs. It’s responsible for helping branches stretch and leaves grow.
Color Temperature: The color temperature of a light (measured in Kelvin, or “K”) shows you what sort of light you can expect to see coming from the bulb. This temperature is an indicator of what wavelengths of light your plants will receive. Temperatures range from 1000k to 10000k, but most fall within the 2000k to 6500k range.
- 2000k to 3000k are known as warm temperatures, giving you yellow/orange light. Yield Lab HPS bulbs are rated at 2100k, which contains the red wavelengths plants need during flowering.
Temperatures over 5000k are known as cool temperatures, giving you a blue/white light. Yield Lab MH bulbs are rated at 5500K, which contains the blue wavelengths plants need while vegging.
- Yield Lab CMH bulbs can shine at around 4100K, which is a brilliant white and contains nearly all wavelengths of light in one bulb.
Lumens: The amount of light a system is pumping out is measured in lumens. The higher the lumens, the brighter the light; and the brighter that light is, the more energy (in the form of light and heat) your plants and growing area receive.
- All plants require different lumen ranges to grow properly, so it’s important to understand how much light your plants need and get the proper grow light for them.
Heat: The chemical reaction that causes HIDs to produce light creates a lot of heat. As such, brighter lights generate more heat. This isn’t necessarily a bad thing, because plants need heat to survive. Too much heat, however, and they’ll suffer big time.
- If you have enough room, air, and ventilation in your indoor growing area, the heat from any size grow light will be a nice addition to your garden’s environment. It’s important to note, though, that lights that are too strong for your growing area will trap in heat and can literally burn your plants.
- Spacial Requirements: HID grow lights need to be hung at a certain height above your plants at all stages of growth. Unlike other forms of light — like T5 grow lights and LEDs that can hang close to plants — HIDs need at least 12 to 24 inches of space above plants for them to safely grow. If you don’t have enough room to keep your lights safely above your plants, you’re going to have a problem.
With all that in mind, let’s explore the components of HID grow lights.
There are lots of considerations when it comes to finding the perfect HID grow light for your plants. In fact, there are three main components you’re going to have to understand in order to make the best decision for your growing needs: the light bulb, reflector, and ballast.
These three components are the foundations of any HID grow room, so we’ll be explaining everything you need to know to choose the right ones for the best yields possible.
The ballast is the brains of any grow light kit. It regulates the amount of energy that lights receive when they’re plugged in and turned on. A ballast transfers the energy needed by a bulb. This energy creates the arc needed to produce light. In fact, the wattage rating of anything grow light-related is referring to the ballast it needs to make it run.
Grow lights wouldn’t be very useful without a ballast, so a dependable ballast is vital for any grow room. Not all ballasts are the same, though. From strength to construction, there are a few key factors to consider when you’re looking into the right ballast for you.
Strength: You’ll want a grow light with a ballast capable of giving your plants the light they need — you don’t want anything too strong or too weak for them. It’s important to consider the strength of a ballast to ensure you have a breaker that can handle it.
- For example, 1000w ballasts usually pull around 9 amps, and the average household has a circuit breaker capable of holding 100 to 200 amps. If you factor in all of your home’s appliances, it’s possible that plugging in a grow light into an outlet will trip the breaker. That means the light you want to use is too powerful for the electricity your household has available.
Digital vs. Magnetic Ballasts: The construction of a ballast plays a big role in how HID grow lights run and how safely they operate. Both magnetic and digital ballasts have advantages and challenges. When you’re shopping for an HID grow light, make sure you pay attention to the type of ballast that comes with it.
Digital ballasts are made with solid-state electronic circuits and microprocessors similar to computers and other electronic devices. These let you adjust the amount of energy your bulb receives from 50 percent all the way up to 110 percent of a bulb’s total power. Digital ballasts have a soft start feature that lets your bulbs warm up instead of being slammed with power all at once, and they adjust to MH and HPS bulbs automatically.
- One downside to digital ballasts is that they produce radio frequency interference. Thankfully, there are EMI filters to help minimize radio interference — but digital ballasts tend to disrupt Wi-Fi, cell phone, television signals while running.
Magnetic ballasts have a core made of steel plates that are wrapped in copper wires. When plugged in, this core creates a magnetic field that produces the energy given to light bulbs. Interestingly, these were the original grow light ballasts and are still tried and true in lots of grow rooms around the world. They’re inexpensive, get the job done, and do so without annoying radio interference.
- The magnetic field created by these ballasts produces a lot of heat. As such, magnetic ballasts run hot and need to be cooled by a fan to make sure they don’t put your grow room in danger.
- Magnetic ballasts are two to three times the size of digital ballasts. These ballasts take up more space in your grow room, which can be a problem if there’s nowhere else to safely mount them.
- A magnetic ballast sends nearly all the energy it gets directly to the bulb. This wears on the bulb and leads to a shorter bulb lifespan.
- These ballasts can’t detect MH and HPS automatically, which means you’ll either need a magnetic ballast with an MH/HPS switch or two separate magnetic ballasts.
- Digital ballasts are made with solid-state electronic circuits and microprocessors similar to computers and other electronic devices. These let you adjust the amount of energy your bulb receives from 50 percent all the way up to 110 percent of a bulb’s total power. Digital ballasts have a soft start feature that lets your bulbs warm up instead of being slammed with power all at once, and they adjust to MH and HPS bulbs automatically.
- Free Ballasts vs. On-Board Ballasts: Regardless of the type of light you use, there are two ways a ballast is used in a grow light kit. Ballasts are either detached from a reflector or connected directly to it, and each style has its advantages and challenges.
- Free ballasts hang free from a grow light reflector. They can be mounted to or placed on any surface where it’s safe to do so, which is great for crowded grow rooms. However, these ballasts add an extra cord to your grow light setup which adds to the clutter of cords throughout your grow room.
- On-board ballasts are attached directly to a reflector. This saves room in your growing area and gets rid of the mess you get with lots of cords. That said, the weight of the ballast will put stress on your grow light hangers, which can be catastrophic for your plants if your hangers break. Due to their size, on-board ballasts often have extremely limited reflector options, none of which are as large as those used with free ballasts.
The next key component to any HID grow light is the reflector. You may not know it by name, but reflectors are used on pretty much all lights, from desk lamps to street lights. A reflector is what keeps light from being wasted by enclosing it and focusing it in a certain direction. In the case of an HID grow light, the reflector is used to focus light down on to your plants.
Choosing the right grow light reflector will ensure your plants get the light they need for the yields you want. There are various reflectors out there to choose from, each with their own benefits for your grow room and plants. Let’s get to it.
Air Cooled Hood Reflector: The two biggest benefits to this reflector are its air cooled shell and its ability to intensely focus light.
- Air cool hoods are made with an intake and an output vent port that lets you connect a duct fan. These ports can be fitted with a high output fan or duct fan to help cool their bulb while it’s in use. This both extends the light of the bulb and helps mitigate the heat your grow room receives from the light bulb.
- An air cooled hood reflector is designed to surround your bulb and focus a limited but strong square of light down onto your plants.
- Cool hoods are great in any grow room situation, from a grow tent with two or three plants to an entire warehouse grow.
- Hoods come in small, large, short, and tall variations, as well as solid hoods without air cooling capabilities.
- Cool hoods have glass lenses that help duct fans cool the bulb. If there’s nothing to cool the bulb, there can be a build up of heat surrounding your bulb. When that’s the case, you can remove the glass lens and let heat travel from the bulb like it would with any other reflector.
Wing Reflectors: Also known as the “bat wing,” these are the most common reflectors — they’re simple, inexpensive, easy to assemble, and highly effective at shining light down onto plants.
- Light hits multiple points across the reflector, which then reflects intense light down onto the plants below.
- The light reflected onto your plants is an intense square of light that’s similar to that of a cool hood, only a little softer.
- These reflectors are great for beginners as well as pros on a budget and are great for growing one to three plants in a closet or up to six plants in a large grow tent.
- The simplicity of the wing reflector may be its downfall, though. These reflectors introduce a lot of heat onto your plants. As a result, you’ll need to cool your growing area the most with these reflectors.
Cool Tube Reflectors: Air cooled tube reflectors can help reduce heat in your grow room and increase the longevity of your bulbs, with the added bonus of being compact.
- The cylindrical shape of these reflectors makes them the most versatile reflectors you can use. There’s no bulky shell like the air cooled hood or wide fins like with wing reflectors, so it doesn’t take up a lot of room in your growing area.
- Light spreads from the reflector and down onto your plants, with small fins on the side to help focus light onto your plants. This results in a surprisingly large coverage area.
- Cool tubes are best for small growing areas like closets and grow tents smaller than 5x5ft.
Umbrella Reflectors: If you have a lot of plants that need light, umbrella reflectors give you the largest coverage area of any reflector around. Not only is their coverage area large, it’s also softer than other reflectors’, which comes in handy for plants that can’t stand intense light coverage.
Like cool hoods, umbrellas offer a distinct shape of light. In this case, it’s a large circle that will give you a huge, soft coverage area.
- Umbrellas can be moved closer to plants than other reflectors, even with higher wattage bulbs. This can greatly increase the intensity of the coverage area.
These reflectors are great for larger grow rooms, grow tents, and large scale grows that require more coverage.
- Umbrella reflectors are at least 30 inches wide, and unfortunately don’t work well for growers with limited space.
- Due to the relatively soft light umbrellas give your growing area, large growing areas may require supplemental light in order to grow plants to their full potential. Don’t worry — supplemental light can be as simple as adding low wattage LEDs, T5 fluorescent lights, or even ceiling lights.
- Like cool hoods, umbrellas offer a distinct shape of light. In this case, it’s a large circle that will give you a huge, soft coverage area.
We’ve talked about how to power an HID grow light and how to focus its light. Now it’s time to talk about the light itself. While all grow light bulbs work the same way, their contents are what gives your grow room different benefits.
HID grow lights work by heating gas and metal salts inside of a glass bulb. When these gases and salts are heated enough, they react by giving off light. That light is powerful and intense enough to help plants perform photosynthesis, which is the basis for all plant growth.
There are two types of grow light bulbs used in the grow room: HPS bulbs and MH bulbs. These bulbs use different types of metals and salts to produce the various wavelengths of light you’ll need to grow plants.
High Pressure Sodium (HPS) Grow Light Bulbs: HPS bulbs are made with xenon, mercury, and sodium. When they’re heated up, they give off a bright orange light. This orange light contains mostly red and orange wavelengths of light that help stimulate leaf and bud growth. In addition to limiting exposure times, these warm wavelengths help trigger your plant’s ability to flower and grow fruit.
- HPS bulbs can be used throughout the entire grow cycle of plants. However, they may have a slightly harder time growing branches, which will result in longer vegging times.
Metal Halide (MH) Grow Light Bulbs: MH bulbs contain mercury vapors and metal halide salts, which are compounds of metals like mercury, silver chloride, and silver bromide. When heated, these chemicals give off a bright white light with a bluish hue. This light contains mostly blue wavelengths of light that are beneficial to leaf and branch growth, and vital for the vegging and beginning stages of plant growth.
- MH bulbs are used mostly for vegging growth and have little effect on flowers. However, with MH bulbs you’ll get taller, wider plants with the potential for higher yields.
Ceramic Metal Halide (CMH) Grow Bulb: CMH bulbs are just like any other single ended bulb — instead of an arc tube made of quartz, though, it’s made of ceramic. This ceramic tube has the ability to use mercury, argon, and halide salts to give you an even spectrum of light that contains more wavelengths of light than both HPS and MH bulbs. A CMH bulb’s spectrum is desired by home growers and large-scale growers because it’s both powerful and optimal at all stages of growth.
- CMH bulbs lack the optimal amount of warm light wavelengths, so flowering with CMH grow lights may take supplemental lighting. However, CMH bulbs come in two color temperatures (3100K and 4200K) to help give you a warmer wavelength for that purpose.
- CMH lights are limited to 315w grow lights and 630w grow lights, and have a limited selection of reflectors to work with.
Single vs. Double Ended Grow Lights
The construction of each type of bulb makes a huge difference in its efficiency on your plants. From the internal pressure to its physical make up, let’s check out the different ways bulbs are made and what it means for your plants.
Single Ended Grow Bulb: These bulbs are the easiest to use and the most reliable, too. The quartz arc tube of a single ended HID bulb contains the gas and salts needed for light. The tube is attached to a metal frame wire that’s connected to each end, holding it in place inside the bulb. The vacuum created by the construction of single ended bulbs helps regulate the temperature of the gases and metals inside, giving you safe, stable light coverage.
- The metal frame and components inside of a single ended bulb limit the amount of light your plants receive.
- The vacuum limits the temperature inside the bulb, which limits the amount of light the bulb’s able to produce.
Double Ended Grow Bulb: These bulbs give you tons of light, which is why beginners and commercial growers alike love using them. The arc tube of a double ended HID grow light is held in place by two wires on either side of the bulb that act as conductors for the electricity that heats the arc tube. This allows the arc tube to heat up more than single ended bulbs with only one conductor, resulting in higher, more intense light.
- These bulbs have no vacuum to protect the temperature of the bulb. This means if cold air hits them — say, from a high output fan or an AC unit — their internal temperature will be thrown off, resulting in inconsistent lighting.
- Mitigating heat can be tricky. You’ll have to find a balance between the right growing temperature in your grow room and the optimal running temperature of a double ended HID grow light.
It’s the moment you’ve been waiting for: It’s time to start figuring out how to choose the best light for your grow room. We’ll set you up with everything you need to know, so all you have to do is plug in the information.
Wavelengths of Light Your Plants Need
The first step to choosing your perfect grow light is finding out what wavelengths of light your plants need. Plants respond to the various wavelengths of light in different ways, and the combination and timing of those wavelengths is what it takes for a plant to grow to its full potential. That’s why it’s vital to choose the right bulbs to power your grow room.
- Make sure your HID grow light has an MH light. All plants go through a vegetatitve stage which requires blue wavelengths of light. That means MH bulbs are pretty much mandatory for all plants, whether they flower or not.
- Fruits, flowers, and buds will need HPS light. Flowering plants and plants that produce buds and fruit will need red wavelengths of light to grow to their full potential. That means flowering plants will eventually need an HPS bulb, too.
- CMHs are a grower’s best friend. If you’re not 100 percent sure what wavelengths of light your plants need, you might want to consider going with a CMH grow light. These lights excel during the vegging stage and need little to no help getting your fruiting plants to harvest.
- Due to the lack of red wavelengths CMH lights offer, you may need a boost from a red LED grow light or an HPS grow light. This will supplement the wavelengths you need to boost flower production to optimum levels.
Reflector and Lumen Requirements For Your Growing Area
After you establish which bulbs you need for your garden, it’s time to figure out what sort of grow light reflector you should use. In addition, you’ll want to determine how much power you need to properly light the plants in your garden.
According to grow experts, leaves convert light into usable energy to grow at around 4000 lumens per sqft. With this lumen requirement, we can use a simple equation to estimate how many lumens a growing space requires: (square feet) x 4000 = lumen requirement for growing space.
Skeptical? We were at first, too, but check out how this calculation works out in real time below.
2x2ft to 3x3ft Spaces: Using the equation above, these spaces will need 16,000 to 36,000 lumens of light to efficiently grow plants. That means you’ll need a grow light that won’t overpower one to two plants in such a small area while still being able to fit inside your growing space comfortably.
- For these spaces, we recommend using 315w CMH grow lights. Bulbs like the Yield Lab 315w 3100K CMH bulb, for example, offer a lumen output of 36,000, which just so happens to be the max they can take.
- Only small on-board hoods and wing reflectors can fit comfortably inside spaces and grow tents of this size.
2x4ft to 4x4ft Spaces: These indoor growing spaces require 32,000 to 64,000 lumens. Most beginner grow tents and small grow rooms with four to six plants run efficiently at these levels.
- For growing spaces of these sizes, we recommend using 400w HID grow lights. Bulbs like the Yield Lab HPS 400w Bulb, for example, have 55,000 lumens and the Yield Lab MH 400w Lamp Bulb has 36,000 lumens. These spaces and tents can utilize bat wing, cool hood, and cool tube grow light reflectors.
- Given the total lumen output of CMHs in a 315w bulb, you can also use a 630w CMH grow light utilizing two 315w bulbs for 62,000 lumens of light.
5x5ft to 7x7ft Spaces: In larger spaces like this, you’re going to need 100,000 to 196,000 lumens of light to fill the space. Serious grow tents and grow rooms with six to ten plants should have the space to alleviate the heat from high powered lights efficiently.
- For spaces of this size, we recommend using one to two 1000w HID grow lights. Bulbs like the Yield Lab HPS 1000w Bulb give you 130,000 lumens of light, and its MH counterpart will give you around 110,000 lumens. Naturally, if you have a larger space, you’re going to need multiple grow lights.
- The great thing about these growing spaces is that cool hood, wing, cool tube, and umbrella reflectors all fit inside these spaces and can be adjusted for optimal coverage.
8x8ft and Larger Spaces: When we get into much larger growing spaces, you’re going to need at least 256,000 lumens of light to grow the 12+ plants these spaces can typically hold.
Spaces this large will need at least two to three 1000w HID grow lights with a cool hood, extra large hood, or umbrella reflectors to get the power you need for your plants.
- Cool hoods will offer plants intense light coverage, but if you have a lot of plants to cover, you’ll need a lot of cool hood reflectors.
- Extra large hoods and umbrellas will give you a huge coverage area to cover lots of plants at once, but the light plants receive may not be as intense as it would be from cool hoods.
- Spaces this large will need at least two to three 1000w HID grow lights with a cool hood, extra large hood, or umbrella reflectors to get the power you need for your plants.
Keep in mind that while these estimates are a great way to figure out how much light you need for your growing space, they’re just that: estimates. There are some caveats to these estimates that you’ll want to keep in mind when lighting your plants.
- Plant Height: Plants need to be at least 12 to 24 inches above plants at all times to avoid light bleaching and physical burns — not to mention increased temperatures that hinder growth. This will be a problem if you grow tall plants and don’t have the height to adjust grow lights to the correct height.
- Canopy vs. Entire Room: The numbers calculated above accurately tell you how much light you’ll need for a room full of plants. But is your growing area stuffed with plants? Probably not, which means you’ll want to measure the sqft of your canopy, which is the area that your plants’ leaves take up.
Note: It never hurts plants to give them a little extra light. Just make sure you’re not overpowering them or using electricity you don’t need to. So just like we did before, calculate the area of your canopy (length x width), and then plug in the numbers. That way you can calculate how many lumens your plants need and avoid paying too much for electricity you’re not using.
Factors That Affect Lumen Output
Just because a bulb is advertised at a certain lumen output doesn’t mean your plants are going to receive that exact number. Here’s why:
- Reflectors hinder light. Lumens are measured without reflectors — once reflectors surround a bulb, the reflected light has fewer lumens than a bulb without reflectors. Glass lenses like the ones you find with cool tubes and cool hoods hinder that light even more. The loss of lumens is minimal and, ultimately, isn’t that big of a loss. Focused light will always have better lumen quality than unfocused light. In fact, the quality and usefulness of lumens is known as the PAR and we’ve written extensively on the subject here.
- The higher your lights, the less lumens your plants receive. Typically, you’ll want 12 to 24 inches of space between your light and your plants to avoid bleaching and burns. Lumen readings for grow lights are usually done around 12 to 15 inches away from plant canopies, so this shouldn’t be an issue. If you go past 15 inches of height, though, you’ll start to lose out on lumens and usable light (PAR) with it.
- Less lumens means a lower PAR rating, but that’s not necessarily a bad thing. Professional growers agree that you’ll need a PAR rating of 400 to 600 for vegging and 600 to 900 for flowering.
- If you have a light like the Yield Lab 1000w HPS Cool Hood that gives you a peak PAR of 1377 at 18 inches above your plants, you can raise it to 24 inches and adjust that PAR to 824 and get a wide, powerful coverage area.
- You can also use a light like the Yield Lab 600w HPS Cool Hood that gives a peak PAR of 900 at 18 inches and raise it to 20 inches to give your plants a less intense but still effective source of light.
- Reflectors also affect the PAR rating of a plant. For example, the PAR on a cool hood is going to be higher than an umbrella reflector because the light is more focused in one area and not spread out over a wide area.
Adjusting Your Lumens and PAR
A quick look at the lumen and PAR ratings of any HID grow light will show you that it’s rare to find exactly what you need. You’ll need to get a grow light that offers close to what you need — whether it’s over or under — and adjust from there. It’s a lot easier than you’d expect and just takes a little bit of creative thinking to pull off.
Utilizing Multiple Grow Lights: Sometimes your plants need so many lumens that using multiple lights is the only solution. When that’s the case, it’s best to figure out how many lumens you need and use grow lights that reach that threshold.
- Chances are you’re going to find lights that will give you either a little less or a lot more light than you need. For example, if you’re in a 7x7ft canopy that needs 196,000 lumens, two 1000w HIDs will give you 220,000 to 260,000 lumens, which is more than enough light for your needs.
Raising/Lowering Lights: If your lights are too strong for your plants or their reflector isn’t able to give your plants the lumens and PAR they need, lowering and raising an HID grow light can help you get the intensity your plants need.
- Lowering your light closer to your plants will increase light intensity and PAR, but will decrease light coverage.
- Raising your light further away from your plants will lower PAR when your light’s too intense. Above 24 inches, though, your plants will start to stretch in an attempt to find light for their leaves.
- Double Ended Grow Lights: If you want a boost in power but need to leave your grow lights at the height they’re at, double ended grow lights can increase lumens and PAR significantly. For example, the Yield Lab Double Ended 600w MH Grow Light Bulb has 85,000 lumens, compared to its single ended counterpart that offers 61,000 lumens.
- Dimming Ballasts: Most ballasts these days have a dimmable feature that allows you to limit the amount of power your bulb receives, which limits the amount of light coming from the bulb. When raising your lights isn’t an option and you need to lower the intensity of your lights, dialing down the power of your ballast can reduce a grow light’s output by 50 percent to prevent your plants from being overwhelmed.
Congratulations! You now have every piece of information you need to make the best decision for your grow room. You know the amount of power that’s best for your growing space. You’re also equipped with the knowledge to pick the type of reflector and the amount of lights you need for your grow room.
Even with all the knowledge at your disposal, though, it can be difficult selecting the perfect grow light. That’s why we asked expert growers what they use in the grow room and came up with five recommendations to fit your needs.
Best Overall Grow Light: Yield Lab 600W HPS+MH Air Cool Hood Reflector Grow Light Kit
What makes an HID grow light like the Yield Lab 600W HPS+MH Air Cool Hood Reflector Grow Light Kit great for nearly any grow room is its power, coverage, and convenience. With the power to give your plants 61,000 lumens during the vegging stage and 90,000 lumens while flowering, a single one of these grow lights can light a 4x4ft garden (minimum of 64,000 lumens) with ease.
The cool hood reflector’s light footprint is focused and intense. Because of its reflective structure, you can raise this kit around 24 inches for a footprint of around 5x5ft with plenty of usable light. At the same time, lowering this grow light kit closer to your plants will increase its intensity much more than other reflectors like wing reflectors and even cool tubes. If you need less intensity, the dimmable digital ballast can reduce the light’s output by 50 percent, allowing your plants to ease into the intensity they receive as they grow.
With a reflector size of 19x17x8in, you can fit this light in nearly any grow tent or grow room needed. It has the ability to be cooled with duct fans, extending bulb life and reducing heat output to your garden. You can also run multiple cool hoods in tandem so you cover huge canopies and grow areas. Whether you’re a beginner starting in a 4x4ft grow tent or a long time grower setting up a 10x10ft indoor garden, this grow light will work well for just about any growing situation.
Best for Professional Growers: Yield Lab Pro Series 1000W HPS+MH Air Cool Hood Double Ended Complete Grow Light Kit
For pro growers who need some serious lighting power, the Yield Lab Pro Series 1000W HPS+MH Air Cool Hood Double Ended Complete Grow Light Kit will give your plants massive amounts of intense light. This doubled ended system gives you 85,200 lumens to veg and a whopping 159,200 lumens for flowering, which gives hardcore growers great lighting for plentiful harvests. Combined with proper nutrition and the right environment, growers can see the biggest yields imaginable.
Just like a standard cool hood, this kit’s reflector creates a limited but focused footprint of light for your plants. Thanks to its double ended technology, the light that comes out of this reflector can reach over 20,000 lumens, making it brighter than its single ended counterpart. Double ended lights also have the advantage of producing more UV and IR that plants need for more vigorous resin, flavonoid, and foliage growth. More foliage means your plants can absorb and process more light and nutrients, allowing them to get bigger and stronger.
Unlike standard hoods, this cool hood reflector has a standing footprint of 21.5x20in, which is easily over 3x3ft of intense coverage when hung at 18 inches. At 24 inches, the loss of intensity is minimal, and if you use multiple lights you can cover areas around 10x15ft or more. So whether you’re trying to grow a few super plants or a whole warehouse full of high quality plants, this grow light will give you pro-level intensity and coverage needed to pull off award-winning harvests.
Best for Beginners: Yield Lab 400W HPS+MH Cool Tube Reflector Grow Light Kit
If there’s one thing beginner growers need it’s wiggle room, and that’s exactly what you get with the Yield Lab 400W HPS+MH Cool Tube Reflector Grow Light Kit. This light will give your plants 36,000 lumens while vegging and 50,000 lumens while flowering — enough to cover two to three plants in spaces like 2x4ft grow tents and 3x3ft closets. Combined with the cool tube reflector, this HID grow light kit gives you a footprint of light that’s both effective and easy on your plants.
Cool tubes direct light downward without focusing it too much, which is a good thing. While more intense light has a higher potential for larger yields, growers can fry their plants with lights that are too strong for their needs. The semi-focused footprint this HID grow lights provides has enough lumens to grow plants without overpowering them with light. With this 400w cool tube system, growers can pull off great harvests without worrying that they’re giving their plants too much light (or not enough, as is the case with umbrella setups).
Not only are cool tubes compatible with nearly any growing space around, they’re highly adaptable to their surroundings. Put a cool tube in a wide growing space and you get a large footprint that can be lowered for intensity without losing significant spread. Put one in a smaller grow setting, and its wide spread can be reflected back at your plants with more intensity than that of a wing reflector. Regardless of the growing area you’re working with, this cool tube grow light can ease you into growing and help you perfect growing consistently larger harvests.
Best for Large Grow Growing Areas: Yield Lab Pro Series 600W HPS+MH XXL Hood Double Ended
Most think that umbrellas would be best for large scale growing, but the Yield Lab Pro Series 600W HPS+MH XXL Hood Double Ended Complete Grow Light Kit will cover a huge growing area with enough intensity to cover six or more plants in large growing areas. Combining 85,000 lumens of vegging power, 96,000 lumens for flowering, and a starting footprint of over 2x2ft, you can bet a few of these lights will cover canopies of 8x8ft.
Like cool hoods, these XXL hoods give your plants a focused footprint of light filled with tons of usable light at only around double the size. You’d think with that size the light wouldn’t be able to keep its intensity, but with double ended grow lights that give you at least 10,000 more lumens, plants will be able to utilize more light than a single ended light would in this reflector.
The unique thing about this reflector’s design is that it offers a more even distribution of light than a smaller cool hood reflector would. When used in tandem with other XXL hoods, the spread of light you receive is both intense and evenly dispersed. That makes the intensity and the quality of the light your plants receive equal across most of the canopy, promoting even and vigorous growth.
It’s tough to ensure plants are receiving all the light they need in a large grow operation. Umbrellas may not give you the intensity you need, and single ended cool hoods may not give you the coverage you want. With this double ended HID grow light and its XXL hood reflector, your plants will get the necessary intensity to flourish with the proper coverage to grow huge harvests.
Best Budget Grow Light: Yield Lab 400W HPS+MH Wing Reflector Digital Grow Light Kit
Rounding out our list of grow lights is the greatest bang for your buck: the Yield Lab 400W HPS+MH Wing Reflector Digital Grow Light Kit. This lightweight and cost-effective HID grow light will give your plants 36,000 lumens of vegging light and 50,000 lumens of light for flowering, which is enough to light a 3x3ft growing space without breaking the bank.
The reflector is shaped similarly to a cool hood and provides similar intensity. With a starting spread of 14x20.5in, this reflector has multiple points of reflection to maximize its limited, focused light footprint with an intensity that’s effective at least 18 inches above plants. Compared to hoods that have enclosed bulbs, wings are partially open which allows the light to spread out more than hoods to make it easier on your plants to receive.
Don’t let the minimal cost fool you — this wing reflector is definitely worth more than its price tag. They’re super easy to assemble and more than effective on any grow, whether you’ve got hundreds of grows under your belt or you’re a first-timer. With their intense coverage and low cost, this is one of the most popular HID grow light kits around.
The tools you’ve gained in this guide will help you choose the right grow light, but knowing what grow light you need for your growing area is just part of the equation. As we come to the end of this journey, it’s important to answer some common yet vital questions all growers ask throughout their HID grow light experience.
1. What bulbs do I need to grow my plants?
HID grow lights — whether they’re single ended, double ended, or CMH grow lights — come with a bulb that contains the light to grow your plants. However, the type of bulb you use will determine the wavelengths of light your plants get, which will determine the type of growth the plant performs. So when you’re choosing your grow light kit, keep these tips in mind when choosing the bulbs that come with it:
MH Bulbs, aka “grow” bulbs, are used for vegetative growth. Nearly all plants need the blue wavelengths of light these give off to grow roots, leaves, and branches. These are perfect for growing vegetables, as vegetables are usually cut down before you’d need to flower them. For flowering plants to grow the branches and leaves, they need flower buds. MH lights give them a boost of blue wavelengths to get them where they need to be.
- If you’re growing vegetables or plan on growing flowering plants, you’ll want an MH bulb in your grow light system.
HPS bulbs, aka “bloom” bulbs, are mostly used for flowering. They contain tons of the red spectrum that promotes vigorous flower growth and bud bloomage once light cycles change from 16/8 to 12/12. Due to their intensity over MH bulbs, you can use an HPS bulb throughout the entire life of a plant. If you think an MH bulb may not be necessary for your grow — or you have an MH and want to properly grow flowers, buds, and fruit — make sure you have an HPS bulb in your grow light kit.
Many grow light manufacturers offer grow light kits with only HPS bulbs, which tend to be less expensive than those with both. Yield Lab, for example, offers HPS grow light kits as well as HPS+MH grow lights.
- Many grow light manufacturers offer grow light kits with only HPS bulbs, which tend to be less expensive than those with both. Yield Lab, for example, offers HPS grow light kits as well as HPS+MH grow lights.
CMH bulbs give you a more even, inclusive spectrum of light that’s capable of growing both vegetables and flowers. Interestingly enough, they have their own type of MH and HPS styles, in the form of 3100k and 4100k color temperatures. However, their high lumen output combined with their even spectrum gives them the capability to grow nearly any plant from seed to harvest.
- 4100k bulbs give your plants mostly blue wavelengths, whereas 3100k has an even mix of blue and red wavelengths. However, because neither of them have an abundance of red wavelengths, their ability to flower plants to their full capability may be hindered.
2. How much should I spend on a grow light?
Ah, the age old question: “Am I really getting what I pay for?” Some believe the more you spend on a grow light, the better it will perform, and thus the better your yields will be. Others believe that the cheapest options are the best because you can compensate for other aspects of light — like intensity or wavelengths — in other ways.
The truth is that the amount of money you spend on an HID grow light all depends on what you need it to do and how reliable you need it to be. This is pretty vague, but to illustrate our point, here are some key things to ask yourself when looking for a grow light:
- Is it powerful enough to grow all of your plants? The stronger a grow light is, the more expensive it is, no matter what quality it may be. Always make sure you’re shopping in the power range you need, and never undercut your plants on light. For example, if you need to light a canopy of 6x6ft, a 400w wouldn’t give you the light you need despite it being much cheaper than the 1000w or 600w you’d need.
- Does it come with everything you need? You don’t want to get your plants ready for vegging and find out that you don’t have the necessary bulbs or equipment to hang your light properly over your plants. The cheaper a grow light kit is, the less it’s likely to include. Before sacrificing costs, take stock of what you have for your a grow light and what you need. If you don’t need hangers or timers, consider less expensive kits. Otherwise, consider a package that includes the accessories and bulbs you’re going to need, like Yield Lab Grow Lights.
- How is the quality of the grow light? This can be tricky to look into because name brands and non-name brands alike can offer quality (and subpar) products. The key here is to look into the components, see if they work for you, and whether or not a warranty is available for them. For example…
- Ballasts: Cheaper grow lights offer magnetic ballasts, whereas more expensive lights will offer digital dimming ballasts. Magnetic ballasts are heavy and tend to get hot, whereas digital ballasts are small and more efficient than magnetics yet produce radio interference.
- Light Bulbs: The lower the price tag, the less lifetime you can expect out of a grow bulb. Make sure the life expectancy of the bulbs you choose work for your grow room. Less expensive lights tend to die out faster than higher quality (and higher priced) bulbs. That said, they’re also cheap to replace, so it’s up to you to determine how long you’re willing to spend on replacements versus upfront costs.
- Reflector: While reflectors may look similar across multiple brands, their construction may vary. For example, the Adjust-A-Wing Enforcer allows you to adjust the reflector’s wings to focus or spread the light’s footprint. The Yield Lab Wing Reflector, however, features simpler construction and only allows for a specific footprint. While the Adjust-A-Wing may seem like the better choice, it’s almost three times the price of a Yield Lab Reflector and doesn’t offer a significant boost of light over it, either. However, if you need wider coverage and love the footprint that wings offer, the more expensive choice would be best.
- Warranty: This one’s crucial. Typically, the less you spend on a light — especially in the higher range like 1000w and double ended kits — the less coverage it’ll provide. Are you willing to take the risk of getting an HID grow light without a warranty? If so, you risk bulbs that burn out quickly, ballasts that simply don’t work, and reflectors that fall apart through no fault of your own. All grow lights eventually need parts replaced, but not before their expected lifespan — if that happens, you probably don’t want to be stuck with the bill.
In all fairness, there are plenty of growers that start out with low-quality kits with no coverage and eventually replace their various components for high-quality ones. They may even replace them with components that offer warranties. When that’s the case, it’s important to think about upfront costs versus overall costs and the longevity of your system. Can you afford to make what could be costly repairs later to save money now, or invest more and have a little more protection with minimal cost replacements?
3. How much electricity is a grow light going to use?
Now this one’s a little complicated because power rates are dependent on your area, how much you use, and how much energy costs in any given part of the year. However, it’s not impossible to get an idea of how much it will cost to run an HID grow light.
- The first step is gathering all the information you’ll need, which includes the kw/h cost of power, the overall wattage that you’ll be running each hour (the wattage of your light), and how many hours you plan on running your system.
- The next step would be figuring out what other equipment you’re going to run in addition to this light. It’s important to note that HID grow lights add a lot of heat to your grow, and you’ll need to combat that. Take the wattage of any fans, A/C units, and even supplemental lighting you’ll need and add these into the equation.
The last step is plugging in the info for calculation. You can calculate power cost the long way, or you can use a calculator like the one you’ll find here. Just plug in your energy rates, your energy consumption, and how long you want to run the system for an accurate idea of your monthly energy costs.
Be mindful of power pricing tiers that will charge you higher rates based on the total amount of power consumption you’re using. Calculate your cost at all tiers of consumption to get the most accurate calculation of your monthly energy costs.
4. How high do I hang grow lights above my plants?
The height you hang your lights will determine the amount of light energy they receive. Too close and your plants can become bleached by light, overwhelmed with heat, and even burnt. Too far and your plants will stretch out, giving you weak branches and fewer leaves. When it comes to hanging your lights, you’ll want to make sure they’re at a height that maximizes consumption without damaging your plants.
The height you hang your HID grow light at will vary depending on its strength at particular times of growth. Here’s an idea of what we mean:
- (400w HID Grow Lights) 12 to 19 inches away from plants.
- (600w HID Grow Lights) 14 to 25 inches away from plants.
- (1000w HID Grow Lights) 16 to 31 inches away from plants.
Grow lights should be placed from 1 to 2.5ft away. This is because plants need various wavelengths and strengths of light at various parts of growth. MH bulbs, for example, don’t put out as many lumens as HPS bulbs, so you have to hang them closer in order for them to work for your plants. Once your plants move into the flower stage and you replace your bulb with a much brighter HPS bulb, you’ll need to hang your light higher in order to avoid burning and bleaching your canopy.
5. How long am I supposed to run an HID grow light daily?
This question is surprisingly simple to answer. You’ll want to mimic the amount of light your plant naturally receives throughout all parts of growth. Not all plants are the same and thus don’t have the same requirements, but generally, most flowering plants run on the same lighting cycles.
Seedling, clone, and vegetative growth require at least 18 hours of MH light each day and 6 hours of darkness. In nature, this is usually in the spring and summer when there is plenty of light out all day.
- Some growers leave vegging plants under 24 hours of light to maximize growth. While this can definitely help set your grow up for explosive harvests, know that bills will be exceptionally high and you’ll need to keep a close eye on plants to ensure they’re not overwhelmed.
Flowering and blooming require 12 hours of HPS light each day and 12 hours of darkness. In nature, this is usually around late summer and fall when light starts to become more scarce.
- More than 12 hours of light will trigger a plant’s hormones to veg instead of bloom, which is why you’ll need at least 12 hours of darkness. Read more about the theory behind flowering light times here.
Of course, this is just an example of plants like citrus fruit and cannabis. Other plants may require different lighting times. Still, the idea here is to understand that in order to grow your plants to their full potential, you’ll need to start by mimicking the type and amount of light your plants receive.
6. How long do HID grow lights last?
The great thing about HID grow lights is that when it comes to longevity they last as long as you can keep up with them. There’s no point in getting a whole new grow light kit because the ballast died or the reflector broke. So while some components may need replacing now and then, HIDs themselves don’t really have an expiration date — you can simply replace their components as needed.
Various components of a grow light kit certainly have shelf lives. For example, most 600w HPS bulbs last around 24,000 hours, and ballasts like the Yield Lab 600w Ballast tend to last at least three years before needing replacement. However, compared to LEDs that are fully electronic and usually do have a certain amount of hours worth of use, HIDs have the ability to keep running indefinitely just by replacing parts when needed.
Essentially, grow lights last as long as the components you’re willing to keep up with. Rule of thumb: Once replacing components outweighs the cost of upgrading your light system, it’s probably time to get a new grow light. When that time comes, just return here and remind yourself what you need to find the right grow light for your grow room.