CFL Grow Lights: The Ultimate Guide

When I first started growing plants indoors and in hydroponic systems, I had no clue what I was doing.

There are a lot of concepts to learn as a beginner to hydroponics, but lighting is by far the most complex.  There are so many different types of indoor grow lights, let alone learning about the properties of light itself and how plants use it to grow.​

I decided to start with the cheapest, most basic types of light out there: compact fluorescent bulbs, or CFLs.​  They’re a great starting light for beginners because they’re cheap, easy to find, and do a damn good job of growing many different types of plants.

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Our Top CFL Picks At Amazon:

• Agrobrite T5 4′ 4-Tube Fixture
• Apollo Horticulture 5-Pack of 2′ T5 Bulbs – 2700k and 6400k
• Hydrofarm Dayspot 26W, 6400K Bulb
• Sun Blaster 26W, 2700K Bulb

So, What Are CFLs?

CFLs vs. Incandescent bulbs | source

CFLs were designed to replace the classic incandescent lamp, ​also known as the lamp that Thomas Edison reportedly failed 10,000 times to create before finally succeeding.

While incandescent bulbs were amazing,  the simple fact is that they burn hotter and waste quite a bit of the electricity we use to power them – putting out 90% as heat and 10% as light.

On the other hand, CFLs can last up to 10 times longer than incandescent bulbs and put out less heat.

They also take less wattage to deliver the same amount of lumen output as incandescent bulbs.

Why Should You Use a CFL Grow Light?

​There are a lot of reasons that beginning and expert gardeners alike turn to CFLs instead of higher-cost lights like high pressure sodium, metal halide, or expensive LED systems.

• Low cost
• Low electricity expenditure
• Easily available
• Highly customizable
• No special fixtures required
• Can be placed extremely close to plants
• Come in many different shapes, sizes, wattages

Types of CFLs

As far as gardening is concerned, there are two main types of CFLs that matter: soft white and daylight.

The different color temperatures for CFL bulbs | source

The main difference between these two types of bulbs is their color temperature.  Color temperature is an extremely important characteristic of lighting for growing plants, because plants require different temperatures of light for different phases of their growth.

For this reason, you should always be using a mix of both types of bulbs if you’re growing with CFLs.

Without both, you’ll be starving your plants of the type of light they need to thrive throughout their entire growing cycle.

The full color temperature spectrum

Here’s a more detailed breakdown of the types of CFL bulbs you can buy:

Daylight (5000K-6500K)

The daylight bulbs are the kings of the vegetative phase of plant growth.  This is the phase where plants are putting out a lot of leaves and growing quickly in anticipation of their flowering phase.

Daylight bulbs and lighting fixtures are the optimal choice for the beginning phases of a plant’s life cycle for this reason, and the save quite a bit of power over using a high pressure sodium or metal halide system during the vegetative phase.

You can also place them quite a bit closer to your plants than you could a lighting system that puts out more heat, so your plants won’t get burned, and the stems won’t stretch out, weakening the overall health of your plants.

Cool White, Bright White (3500-4100K)

Bulbs in this range are in the middle ground, and are often not very optimal for either the vegetative or flowering phase of a plant’s life cycle.  I recommend staying away from lights in this range, or just using 1-2 in supplement to bulbs in the other two ranges.

Warm White, Soft White (2700-3000K)

Bulbs in this range are optimal for the flowering phase of a plant’s life cycle.  This warm light mimics the state of the sun when most plants are flowering and spreading their seed for another generation of plants to begin growing.

Best CFL Bulbs

You have two options when you’re growing with CFLs: use separate bulbs and build your own system, or go with a lighting fixture.

If you are going with separate bulbs, you need to be aware of one important fact:

CFLs are advertised with a true wattage, and an incandescent equivalent.​

You’ll see something like this when looking for bulbs:

“23 Watt Energy Smart CFL – 100 Watt Replacement”

Ignore the replacement watts and look at the true wattage – this is what you want to base your buying decision on.

Best Soft White CFL Bulb

The MaxLite is the best soft white CFL bulb right now. It’s a bit pricey, but quite efficient and does a great job during the flowering phase for most plants. Keep in mind that you’ll need to buy at least 4-5 of these to get enough light intensity to actually produce flowers and fruits on your plants.

Best Daylight CFL Bulb

The Agrobrite FLC26D is the best daylight or vegetative CFL bulb right now. They’re a long-time favorite of mine due to their consistency in putting out high-quality products. You’ll need at least 4-5 of these to have enough light output for a quality vegetative phase, but it’s worth the money as these are relatively cheap.

Best CFL Grow Lights

For many people – beginners especially – it makes more sense to go with a CFL fixture.  They’re already setup for you so you don’t have to connect a bunch of bulbs together to get your garden going. This saves you not only a lot of time, but a good amount of headache and frustration if you’re not used to building your own lighting setups…and let’s be honest, most of us aren’t familiar with that skillset.

If you’re just starting out, the best CFL grow light on the market is the Agrobrite 2′, 4-Tube T5 Fixture.  It comes with four 2″ long T5 bulbs in the 6500K range – perfect for getting plants through the vegetative phase of the growth cycle.

Because it doesn’t come with any 2700K bulbs and you will eventually want your plants to flower (unless you’re only growing leafy greens), you may want to pick up some extra 2700K bulbs so you can switch a couple out once your plants are ready to flower.

Apollo Horticulture offers an affordable pack of four 2″ T5 CFLs in the 2700K range.

For even more recommendations, see my T5 Grow Lights Guide.

How Many Bulbs or Watts Do I Need?

There’s no good answer here for every situation, so the general rule of thumb is that more light is better.

I like to start at around 100 watts per plant that I am growing, but some plants require less light.  For example, if I’m setting up an indoor lettuce garden, I wouldn’t need as much light because lettuce is a fast-grower that only goes through the vegetative phase (we don’t eat lettuce flowers).

Remember, these suggestions are based on true wattage, not the incandescent equivalent that most CFLs are advertised with.

You’ll be able to tell if you need more light in your garden if you have underwhelming growth in certain areas on your plant, or if your system isn’t adequately covering all angles of the plants.

Remember, we’re trying to mimic sunlight as best as possible, and sunlight moves and covers most plant angles with quite a bit of light as the day goes on.​

How to Use CFL Grow Lights

Now that you know just about everything you need to know about CFLs and you’ve got some for your garden, let’s learn some best practices.

CFLs have a major advantage over other types of lightbulbs in that they plug into normal light sockets.  They also come in various shapes and sizes, so they’re endlessly customizable.  Take this into account when deciding how to arrange your CFLs.

Where to Place Your CFLs

Light is emitted from every angle of the bulb, so to get the most out of them try to have as much of the bulb pointing at your plants as possible.

For the spiral CFLs that I have recommended, a lot of light comes off of the sides as opposed to the front, so you may want to align the sides facing the plants instead of a traditional top down setup.

Try to keep your lights anywhere from 4-6 inches away from the surface of your plants.  Read up on the inverse square law for light if you want to understand why.

Consider Using a Reflector

Because a lot of the light in any lighting system is pointed away from a plant, gardeners use reflectors to harness this wasted light and redirect it toward their plants.

If you don’t have a reflector, using aluminum foil, white paint, or panda paper are also good alternatives.

More Info: Grow Light Reflector and Hoods Guide

I hope this was a good primer on using CFLs bulbs for hydroponics, aquaponics, or any other type of gardening!