Is it time to update your grow light fixtures? Are you looking for a new grow light system? In both cases this post will provide you with all of the information you need to make the best choice.
LED lights have come a long way and if you are buying a new light today, LED is the way to go. They last a long time and provide a good level of light at a very low electrical cost. They are good for you, your plants and the environment.
If you already have a florescent grow light, consider replacing the bulb with an LED bulb that fits in your existing fixture.
LED Grow Light Options
There are hundreds of different lights available and the market is extremely confusing for consumers. This post will try to simplify things for you.
Before looking at specific lights you need to make a significant decision. Are you going to buy a cheaper LED shop light system, or a special LED grow light?
Both systems work for growing low-light plants such as seedlings, lettuce and African violets. Plants that require high light are best served with a special LED light.
LED Shop Light: Option A
The shop light is usually a 4 foot fixture that holds two or four bulbs. These have been the work horse for home grow systems and continue to offer good value. They are even better outfitted with LED lights and are available for T12, T8 and T5 fixtures.
- Low cost.
- Allows you to use existing fixtures and shelf setups.
- Provides a pleasing white light.
- Good for starting seedlings and growing low light plants.
- Bulbs are replaceable in most systems.
- You can mix and match bulbs to improve the quality of light.
- Don’t provide the ideal light spectrum for plant growth, so some of your energy is wasted producing more green-yellow light than your plants can use.
- Provide lower light intensities so they are not the best option for high light requirements such as flowering orchids and growing taller plants like marijuana.
LED Specialized Grow Lights: Option B
These lights come in various sizes, but most are small rectangular units with each unit housing many LED bulbs. The mixture of bulbs in each fixture provide both a higher light output and a better quality of light, than traditional shop lights.
- A good quality fixture will provide a light spectrum that matches the light required by plants. This means that electricity is not wasted producing light the plants don’t need.
- Most units produce higher light levels than shop lights.
- More expensive. Units start at around $200 and go up to over $1,000.
- Light tends to be more purple and less pleasing to the eye – they are production lights, not viewing lights. Some units do produce white light.
- LED bulbs are usually not replaceable.
Which LED is Right for You?
If you want a reasonably priced option and use it for growing low light plants like seedlings, the shop light option is a good choice. If you want the best lights available, purchase an LED light specifically made for the job.
The rest of this post has been broken into two sections; one for shop lights followed by one for specialty lights.
Option A: Understanding LED Shop Lights
LED shop lights are manufactured for humans, not plants. That explains why the specifications and data needed to evaluate the light for plants are almost never available.
Watts don’t really tell you how much light is being produced, even though many people think that a higher watt LED bulb produces more light. I have discussed this in detail in LED Grow Lights – The Myth About Watts.
Lumens is a measure of the amount of light, but it measure the amount of light we humans see, not what plants use. We see green and yellow light much better than red and blue. Plants want more red and blue, than green and yellow. So lumens is not a good way to compare bulbs, but in general more lumens ‘might’ be better.
The temperature, or Kelvin reading, gives an approximate idea of how much yellow and red light there is, but without seeing the actual spectra, this information is also not of much help. People have been growing plants under cool white (4000-6500 Kelvin) and warm white (3000 Kelvin) for years; both work. The cool whites work great for seedlings and the warmer light helps a bit for flowering a plant. If you have an option, the best solution might be one of each bulb in each fixture.
Light from the sun at noon is about 5,000 Kelvin, but it is a myth that sun light is best for plants – its not.
The specifications you really want to know about LED lights (see below) are rarely available for shop lights.
So how do you select the best LED bulb? The reality is that most of these bulbs will perform about the same. Try to pick one with higher lumens, more individual LED bulbs, and a name brand. With LED, quality does matter.
Upgrading Existing Florescent Lights to LED
Your existing fixture is probably using florescent bulbs. To make these work, the fixture has something inside called a
ballast. It is usually covered and looks like a rectangular box with wires coming out of it. This is required to make florescent bulbs work, but it is not required for LED bulbs.
Manufacturers provide two different options for upgrading your current fixture.
Ballast Compatible LED
‘Plug and play LED’ lights are designed to work with the existing ballast which makes them easy to install. Just remove the florescent bulb, and add the new LED one. Perfect for the non-handy person.
The downside to these bulbs is that they are more expensive and less energy efficient because the ballast is still using up electricity, even though is is not required. You also need to be sure that the bulb and ballast are a match. Not all brands of bulbs work in all types of florescent fixtures.
‘Retrofit LED’ are bulbs that fit the standard fixture, but require you to remove the ballast. This is a bit more complicated and requires some simple wiring. This video shows you how it’s done. Caution – I have not done this myself, so I don’t know if the video is correct, but it seems to match the procedure in other Youtube videos.
If you can’t see this video try this link: https://www.youtube.com/watch?v=Zjw2UXVJaS0
The benefit of this option is that the ballast is no longer wasting electricity.
Understanding LED Grow Lights
There are many myths around LED grow lights and I have dealt with these in more detail in the following post.
The rest of this post will discuss things you should consider when selecting an LED grow light.
Quality LED Manufacturer
One problem with LED is that they all look the same to a consumer and therefore it is impossible to ‘see’ quality in a product. Because of this, and the fact that the technology is moving ahead at lightning speed, there is a wide range of quality products out there.
Older technology and lower quality result in cheaper lights. To some extent, you get what you pay for. Unfortunately, manufacturers also try to sell you of features that you don’t need and that increases the price. This has led to many myths about LED lights.
A good idea is to look for a guarantee of more than one year. These things should last 10 years for most home owners so why do manufacturers not give you a 10 year guarantee? I’d settle for three years.
If you want the best, latest technology, be prepared to pay a high price. Most people don’t need this and a mid-range price will give you a good quality product.
Getting the Right Color Spectrum
This is one of the most important considerations. I have dealt with LED color spectrum extensively in another post. In summary, you want the color spectrum of the light to match the light used by plants. It is best to see the actual spectrum of light produced and manufacturers should be providing them. You want lots of red and blue, and some green and yellow.
Intensity of Light
Light intensity is not a major consideration for seedlings or low light plants, but it is important for larger plants and for flowering plants. You want as much light as you can get for the price, provided it is the right color.
Forget about watts and lumens. You want a high PAR, or more correctly, a high PPDF value. Manufacturers mix up these two terms. A higher value means more light intensity of the color wavelengths used by plants.
As a general rule:
- 100-300 PPDF for seedlings
- 200-600 PPDF for vegetative growth
- 600-1,000 PPDF for flowering
- 800-2,000 PPDF for real sunlight (depends on elevation, location etc)
- 160 – 400 PPDF (80% less) in full shade
If a light is putting out over 800 umol.m.2s1 of (PPDF) PAR in the center of the light it can burn your plant.
Watts of LED Bulbs
The individual LED bulbs inside and LED light can have various wattage ratings. The best bang for the buck today are 3 watt bulbs – a good compromise between light produced, heat produced, longevity and cost. They are not the latest technology but they are well established and reliable.
Footprint = Area Covered
Most LED grow lights are quite small units, usually less than a foot square. But to be useful, we want the light to cover a large area because that means more plants can be grown under each light.
The useful area that is covered depends on the intensity of the light, the design of the bulb lens (cover over each LED bulb) and the design of the housing. This is all complex and the only way for you to compare two products is to look at their light distribution profile, as shown here. It should show the PAR or PPDF values at various distances from the light. Showing you LUX or Lumens is useless. This should also include distances out to the side of the light, not just directly underneath it.
Most home owners use light stands and they tend to be long and narrow. This design works well with shop lights that are long and narrow, but it also fits more easily into home grow areas – like the furnace room. If this is the kind of setup you plan to use, you want a long, narrow LED.
Unfortunately the LED grow lights are mostly square, or slightly longer than wide. That is a problem because the ends of your grow area will not get enough light. The industry seems to be producing these lights for large grow rooms that use many lights in a row; not for home owners.
The solution is to buy two smaller units and set them up to cover the longer space, but that costs more money.
Some of the more expensive units offer a switch to go between vegetative growing and blooming. This switch toggles blue and red lights on and off to make the light more suitable for the type of growing you are trying to accomplish. This makes sense from an energy efficiency point of view – why run red LEDs when you don’t need them?
But is the extra cost worth it? Keep in mind that switching some bulbs off reduces the intensity of light – does that produce as much plant growth? As a gardener, I would skip this option.
The watt rating for an LED lamp is for the whole unit and does not directly relate to the amount of light produced. It does however tell you how expensive it will be to run the light since you pay for each watt-hour used. A lower watt value is less expensive to run.
Fans use extra wattage, but keep the unit cooler, which should result in longer LED life. This wattage is included in the watt rating of the unit.
Which LED Light is the Best?
I am not going to begin to provide a specific brand. The brands mentioned above are included in this post because their web sites provide pictures and specifications which you need to see to buy a product. Most manufacturers don’t provide this information. Does that make them the best? Maybe not, but at least they are honest and know what they are talking about.
This morning I received a request from another manufacturer to include them in my LED posts. Their definition of PAR on their web site is wrong. They provide no spectras, and no light distributions. How can anyone evaluate their light? It might be the greatest one on the market, but as consumers, we can’t reach that conclusion without the right data.
Providing spectra and light distribution tells me that the company is at least honest enough to show me their data.
There are many suppliers. Don’t buy from the ones who don’t know anything about their product (ie the ones who use myths to sell their product),or the ones that don’t provide the necessary specifications.
Other Posts on LED Lights