Beginner’s Guide to Grow Lights

By: Chris | Last Updated: January 11, 2021

If you’re new to indoor gardening, selecting grow lights can be a serious pain in the butt. You don’t know what’s good, you don’t know what you need, and there are literally thousands of options to choose from. Couple that with all the conflicting opinions you’ll find scattered across the internet and the task seems daunting.

The good news is, it’s not really all that complicated to get started. Lighting options exist because they fill specific needs. The best thing you can do is have an understanding of your specific needs. 

Understanding how your indoor garden will be set up or laid out can go a long way toward helping you select the appropriate type and intensity of lighting.

Take a couple of minutes to think about how you plan to grow indoors, and then I’ll try to explain each lighting style so you can select the type that best fits YOUR needs.

Lighting to Fit Your Needs

The more you know about your needs, the easier it is to make smart decisions about things like lighting. The sub-topics below will help you get to know your needs a little better.

Plant Needs

Different wavelengths, or spectrums of light, produce different results in plants. For instance, flowering plants have a vegetative phase and a flowering phase. Each phase is triggered by different wavelengths of light.

Before you select a grow light, it’s a good idea to make a list of plants you want to grow. Once you have a list of plants, go through them and identify if it is a vegetative, flowering, or fruiting plant.

Example:
Lettuce – Vegetative
Spinach – Vegetative
Tomato – Vegetative, Flowering, Fruiting
Zucchini – Vegetative, Flowering, Fruiting

If you’re planning to grow primarily vegetative plants, you won’t need to be as concerned with finding a full-spectrum grow light. On the other hand, if you want to grow flowering and/or fruiting plants, a full-spectrum grow light will best suit your needs. 

Full-spectrum light can be achieved with fluorescent and HID systems by using different bulbs at different stages of the plant life-cycle. Bulb choices are covered in each lighting section below.

In nature, plants rely on sunlight as a key component for growth and overall health. Indoor hydroponic plants have the same needs. Instead of sunlight, they’ll be relying on hydroponic grow lights.

Hydroponic System Configuration & Distance From Plants

The footprint and vertical orientation of your hydroponic system also help make a decision about lighting. If the growing area of the system has a footprint of say 2’x4’, then you’ll want to use a lighting source that can provide even lighting to the same size area.

Another consideration is shelving. Using shelving systems to grow plants is becoming very popular. In this type of layout, grow lights are fairly close to the plants. For this kind of system, fluorescent lights are normally the best choice since they can be used very close to the tops of plants without burning them.

If you’re growing in a tent or other confined space, heat from lighting is another factor to be aware of. If you use lights that generate higher levels of heat, exhaust fans will be needed to keep the tent from overheating.

Cost

Cost always plays a role when selecting any kind of component. If you’re just getting started in hydroponic or indoor gardening, don’t worry about buying the biggest and baddest light around. A light that checks all the blocks for your needs, including price, will keep you growing for a long time.

Initial Cost
The initial cost is an important factor, it’s the cost you’ll incur up-front when choosing a lighting source.

Operating Cost
A cost that is sometimes forgotten in planning is the operating cost of the grow light. Grow lights run for extended periods every day. The more efficient the light is, the less it will cost to operate it every month.

Maintenance Cost
With the exception of LED grow lights, you’ll want to include replacement bulb cost as part of your initial planning. It’s a good idea to keep several replacement bulbs on-hand so your plants won’t be stuck in the dark when a bulb burns out.

TL:DR – Quick Grow Light Comparison

If you’re looking for the highlights, here ya go!

Fluorescent Grow Lights

LED Grow Lights

HID Grow Lights

Grow Light Comparison Table

Fluorescent LED HID
Initial Cost Low-Moderate Moderate-High Moderate-High
Monthly Cost For a 2’x4′ Area 4 Bulb T5 HO $16.50/Mo 100w LED $7.60/Mo 250w HPS $22.00/Mo
Heat Output Low Low Moderate-High
Vertical Space Low Low-Medium Medium-Large
Complexity Simple Simple Moderate
Replaceable Parts Yes No Yes
Light Penetration Average Good Excellent
Grow Area Small-Large Small-Large Medium-XXL
Full-Spectrum W/ Multiple Bulbs Yes W/ Multiple Bulbs

Grow Area & Heat Output By Lighting Type

Grow Area Distance From Plants Heat Output
2′ T5 FL (2 Bulbs) 1.5’x2.5′ 3″-24″ Low
2′ T5 FL (4 Bulbs) 2’x3′ 6″-24″” Low
4′ T5 FL (4 Bulbs) 2.5’x5′ 6″-36″ Low
4′ T5 FL (8 Bulbs) 4’x6′ 12″-36″ Low
100w LED Panel 2’x2′ 12″-24″ Very Low
200w LED Panel 2’x4′ 18″-36″ Very Low
400w LED Panel 5’x5′ 18″-36″ Low
250w HID MH/HPS 5’x5′ 28″-48″ High
400w HID MH/HPS 5’x5′ 28″-48″ High
600w HID MH/HPS 6’x6′ 32-48″ High
400w HID MH/HPS 1.5’x1.5′ 3″-16″ Very Low
125w CFL Bulb 2’x2′ 6″-22″ Low

Types of Indoor Plant Lighting

Now that you know what you need in a light, let’s go over some of the characteristics of several lighting choices. 

Fluorescent Grow Lights

Fluorescent lights are by far the least expensive choice when shopping for hydroponic grow lights. They don’t produce full-spectrum light but are very capable of growing hydroponic plants. Since they don’t generate a lot of heat they can be placed close to plants, which makes them an ideal choice if your garden has height limitations.

Fluorescents are a perfect choice for shelved gardens and any other configuration with height restrictions.

Fluorescent lights are omnidirectional, meaning they emit light in a full 360-degree pattern. This is not incredibly efficient since around 50% of the light they produce needs to be reflected back down toward the growing surface. With a good reflector and bulbs, fluorescent lights are still a great choice.

Tube-Style Fluorescent (T5)

For Herbs & Microgreens
VIVOSUN 6500K 2FT T5 HO Fluorescent Grow Light Fixture
$59.85
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06/12/2021 03:48 pm GMT

A long-time favorite of hydroponic and indoor gardeners is the T5 tube-style fluorescent light. Several companies make high quality T5 light systems specifically designed for growing plants. They are relatively inexpensive fixtures, even for larger coverage areas.

The fixtures and ballasts are important, but not nearly as important as the bulbs. Buy decent fixtures, buy great bulbs.

T8 vs T5 Grow Lights

Hydroponic grow lights run for several hours every day, normally at least 12 hours. With that in mind, you want to get the most light for your money. T5 bulbs currently produce more lumens/watt than comparable T8 bulbs.

Bulb Color Temperatures
Vegetative – 6500k
Fruiting/Flowering – 3000k

As a hydroponic gardener, the two bulb color temperatures you need to be aware of are 6500k and 3000k. Leafy greens and flowering/fruiting plants in the initial vegetative phase will perform best under 6500k bulbs. Once it’s time to flower and/or fruit, switch to 3000k bulbs for optimal growth.

Bulb Storage

Make sure you have a suitable area to store additional bulbs if you plan to use T5 lighting. The bulbs aren’t incredibly bulky, but they do need to be stored in a place where they won’t get broken.

Note: If for some reason you come across T12 fluorescent lights, don’t waste your time buying them. They are extremely inefficient and aren’t even legal to produce in the United States of America since 2012.

Compact Fluorescent Lamp (CFL)

Budget Bulbs
Satco S7336 - Spiral CFL 5000K - 120V Bulb Satco S7336 - Spiral CFL 5000K - 120V Bulb
  • 40w bulb
  • 2600 lumens
  • Use 3 bulbs with a reflector, 4-6" above plants for optimal results.
  • Can be used to grow herbs, microgreens, and leafy greens in small spaces.

Compact fluorescent lamps are a replacement for incandescent bulbs. They are what you screw into a normal light fixture. With the right reflector and ballast, they can make an affordable and decent performing grow light for a small setup.

Like tube-style fluorescents, CFLs are available in 6500k and 3000k bulb temperatures.

If you are starting out with only a plant or two, a compact fluorescent can be a very cost-effective way to test out your first grow light.

Fluorescent Pros & Cons

Light Emitting Diode (LED) Grow Lights

My Personal Favorite
SPIDER FARMER SF-1000 LED Grow Light SPIDER FARMER SF-1000 LED Grow Light
  • Full-spectrum light
  • Dimmable MeanWell driver
  • Samsung LM301B LEDs
  • Can be daisy-chained to multiple SF-1000's
  • Enough light to support a 2'x4' garden

This is hands down my favorite LED grow light for beginners. The quality is amazing and you can't find better coverage for the price. It's more than capable of growing light-loving plants like peppers and tomatoes.

LED grow lights have become extremely popular in recent years. That popularity has helped drive the cost down slightly. Higher quality LEDs can deliver full-spectrum light to a hydroponic garden making them a viable choice for all types of plants. Along with that higher quality comes a higher price.

The only LED light under $100 that I trust is the Mars Hydro 600. It is a no-frills product that will illuminate a 2’x2’ grow area nicely and can be used from germination all the way through flowering and fruiting. Running this light 18 hours a day will cost roughly $8.00 per month.

Mars Hydro 600 Grow Lights on Basil
One of my Mars Hydro 600 grow lights shining on basil seedlings.

Being directional, LEDs emit light in a 180-degree pattern toward the surface area they are facing. By comparison, bulb style systems such as fluorescents emit light in a full 360-degree pattern and rely on high-quality reflectors to redirect light toward the growing area. 

Their upfront cost is higher than most other lighting solutions, but they are extremely efficient. When I switched over from fluorescents to LED my electric bill dropped by around $10 per month. 

LED lights generate more heat than fluorescent lights, and normally cannot be placed closer than 14” from the top of plants. If you plan to use a shelving system, this type of lighting is probably not the best fit.

When an LED panel goes out, it’s time to buy a whole new light. That makes its replacement cost a lot more expensive than a fluorescent light system.

LED Pros & Cons

High Intensity Discharge (HID) Grow Lights

Entry Level HID Grow Light
iPower 400 Watt HPS MH Grow Light System Kit iPower 400 Watt HPS MH Grow Light System Kit
  • Digital - Dimmable
  • Works with MH & HPS bulbs
  • Wing reflector
  • Coverage: 4'x4' Veg - 3'x3' Flower/Fruit

High intensity discharge (HID) grow lights are an efficient way to provide light to a large number of plants with a single light. Depending on the wattage, a single HID light can effectively light an area that would otherwise take several LED or fluorescent lights. 

HID grow lights are comprised of a bulb, a hood/reflector, a ballast, wiring, and often an inline fan with ducting to evacuate heat from the growing area. Assembling a HID grow light system is a little more complicated than using fluorescents or LED lights.

This type of system often requires as much as 5’ of vertical space, due to the heat created by the light. This is a major factor to consider if space is a concern.

In terms of light output, a single 400w high pressure sodium HID bulb is comparable to 10 54w T5 high output bulbs. This single bulb generates the same light output as 10 T5 bulbs and does it with 140w less power.

For the average hobbyist growing herbs and leafy greens, HID lighting is overkill unless you have a very large grow area.

Because of their intensity, HID lights are very successful at penetrating the upper canopy of plants, providing quality light to the lower leaves. The most common types of HID bulbs are high pressure sodium (HPS) and metal halide (MH). 

The components of high quality HID systems are expensive, but their light output makes them very competitive against the equal light output from fluorescents or LEDs.

Note: If you plan to use HID lighting, make sure to buy a system that can use both HPS and MH bulbs. Otherwise, you’ll need a ballast for each bulb type.

High Pressure Sodium (HPS)

HPS bulbs produce a yellowish light that is best suited for use during the flowering and fruiting phase of a plant’s lifecycle. Many growers opt to use HPS bulbs all the time, but it’s worth noting that this can result in leggier plants. If you’re mainly growing leafy greens, a metal halide bulb will create bushier, shorter plants.

HPS bulbs are more efficient than MH bulbs.

Metal Halide (MH)

For lush green plants like spinach and lettuce, metal halide bulbs are the way to grow. Leafy green plants seem to respond better to this bluish light. Though it’s less efficient than the HPS bulb, it is a better option if you plan to grow produce that doesn’t fruit or flower in order to develop the edible part of the plant.

HID Pros & Cons

Which Light Style Should You Choose?

Spider Farmer SF-1000 growing lettuce and spinach
Spider Farmer SF-1000 growing lettuce and spinach.

That decision is up to you. You know your needs better than I do, but I hope this article provided you with some insight into the different styles of lighting available for indoor gardeners.

Okay, you talked me into it. I’ll tell you my opinion on these lights.

If you’re growing on shelves, or have vertical limitations go with a T5 fluorescent light in a length and width that fits the footprint of the growing area.

If you are not limited on height and have a growing area of less than 10 square feet, I’d recommend a good LED grow light.

If you have a large grow area, or plan to grow plants requiring a LOT of light go with HID lights. I’d also go with HID lighting if you are planning a large vertical garden, such as along the wall of a basement.

Personally, I use a mixture of LED and fluorescent lighting. My larger grow areas have LED lighting, as do my hydroponic pepper plants. For herbs and microgreens I use fluorescent lights.

Chris Cook started Happy Hydro Farm to share his passion for hydroponic gardening! Growing your own food is incredibly rewarding both physically and mentally. His mantra - "Take excellent care of your plants, and your plants will take excellent care of you."