Growing indoors may seem like a simple task, but emulating the suns natural strength and ability to achieve optimum growth is challenging. The different temperatures surrounding your plants and the intensity trigger release of chemicals that move the plants through their life cycles. The goal of this article is to help you, as a grower, develop a fundamental understanding of the lighting available on the market and which best fit your needs. The common types of hydroponic lighting that will be discussed are: High Intensity Discharge (HID), LED Grow Lighting, Fluorescent Grow Lighting, and Plasma Grow Lighting.
High Intensity Discharge (HID) Grow Lighting
High Intensity Discharge (HID) lights are the most popular choice for indoor growers. HID lamps are typically used for lighting large areas such as warehouses or streets due to their high light output. In order to get started with HID grow lighting you will need three things. First is a ballast which holds and provides a consistent stream of electricity through the bulbs. Next is a reflector which is used to evenly distribute light and heat emitted from bulbs to control for heat spots. This also reduces the need for multiple bulbs.
Finally you will need one of two types of bulbs depending on your gardening goals. Typically bulbs used for indoor gardening purposes will be rated as either 400W, 600W, or 1000W. Several other wattages are available as well. Ensure that you select a bulb that’s compatible with the wattage your ballast provides. The two best HID lights for indoor gardening are high pressure sodium (HPS) and metal halide (MH). Each type of light has strengths and weaknesses.
Metal Halide (MH) Bulbs
MH bulbs are towards the blue/white end of the light spectrum, which imitates the hotter summer sun providing healthy, vigorous growth. This type of light produces stocky, strong plants with dense, green foliage. This bulb should be used after the initial germination of your seedlings when your plants need very warm temperatures. After a certain amount of time, growers often switch to HPS bulbs (which we’ll get to in a moment). Although this is generally the case, some plants, such as leafy vegetables and herbs, can grow to maturity solely using MH bulbs. Some special metal halide lights created for horticulture now even come with an enhanced red spectrum optimum for producing fruit. Be sure to check before purchasing that the halide bulbs you chose are for indoor gardening.
Interested in MH lamps? Check out our selection!
High Pressure Sodium Bulbs (HPS)
HPS bulbs emit a concentrated white light in the orange/red spectrum. This color spectrum is used to imitate the warmer colors of autumn and fall and enhance plants’ reproductive processes for the flowering stage of a plant’s life cycle. This means that the plants respond to the autumn light and produce larger harvests of high quality fruits, vegetables, and flowers. However, when used solely as a light source, it causes plants to become leggy, with larger spacing between branches.
Interested in HPS lamps? Check out our selection!
If having a separate ballast for both HPS lighting and MH lighting doesn’t appeal to you, conversion bulbs may be a possible option. Conversion bulbs come in either “HPS for MH ballasts” or “MH for HPS ballasts.” These unique lamps, as their name suggests, allow you to utilize your ballasts for your plants’ vegetative and flowering stages. Simply run the MH lamp during the vegetative stage, then swap over to your conversion bulb for the flowering process. As always, ensure that the lamp you’re purchasing is rated for the same wattage as the ballast you’re running.
Depreciation and Misleading Specifications
There are two specs that bulbs tout that are often misleading, initial lumens and bulb life. Initial lumens are the number of lumens you should expect the first time you turn on a brand new bulb. Unfortunately this number doesn’t stay consistent with the lifespan of the bulb. With HPS bulbs, you can expect at least a 10% drop in lumens after running for 1500 hours.
If you run the numbers against the specified bulb life, you’ll realize things don’t really add up. Chances are the amount of lumens you’d be getting out of a lamp after running for the given bulb life would not provide your plants the PAR, or usable light energy, they need. Unfortunately, MH bulbs are even worse than HPS bulbs when it comes to depreciation. Expect MH bulbs to depreciate in power as much as double that of HPS bulbs in the same amount of usage.
Solutions to Depreciation
There are only a few options available to get a better lifespan out of your HID bulbs. One solution starts at your ballast. Traditional magnetic ballasts provide a steady stream of power to your bulb throughout its lifespan. Naturally, as your bulb ages, the bulb will lose light energy as time goes on. However digital ballasts can make up for this light energy loss. Digital ballasts recognize when your bulbs aren’t emitting the lumens they’re supposed to and send more power to the bulb to make up for energy depreciation. Of course, what this means is you’ll be expending more energy to keep your lamps powered, but at least you get a better lifespan out of them.
The other option to extend bulb lifespan is to simply invest in higher quality bulbs. It seems there are two types of parties out there. One prefers to replace cheaper bulbs more frequently, the other prefers to spend more on higher quality bulbs and get more power out of the bulbs for a longer period of time. Realistically you probably come out about even financially with one method or the other.
LED Grow Lighting
LED, which stands for light-emitting diode, is a relatively new type of indoor lighting system. This type of lighting is initially more expensive but lasts much longer in comparison to other hydroponic lighting. However LED systems are all-in-one, meaning there’s no need to purchase a ballast or reflector.
Not only can LED bulbs last for years (in comparison to MH & HPS), but these bulbs emit far less heat which means they are ideal for small growing spaces. Typically in setups such as these, the bulbs are much closer to the plants, and heat could have a negative effect on the plants. Unlike MH and HPS bulbs, some RGB or Multi-color LED lighting can emit different spectrums of light. What this means is that higher-quality LEDs will have a “vegetation” mode and a “flowering” mode that can be toggled with the flip of a switch. This is much more convenient than changing bulbs in a HID setup when it’s time to enter the flowering stage. This helps produce optimum efficiency in the different stages of a plant’s life cycle.
The lifespan for LED grow lighting varies, however they have a range of somewhere from 50,000-100,000 hours of use. This is a lifespan of five times longer than traditional HPS/MH setups, which might have a max lifespan of 20,000 hours.
How LED Power Corresponds to Wattage of Traditional Grow Lighting
There tends to be some confusion determining how powerful your LED is relative to traditional high intensity discharge lighting. The wattage specified on your LED lights isn’t necessarily the amount of watts that will be used when running. An LED rated at 1000W means that’s the maximum amount of power the LED is capable of handling. If you juice an LED with that amount of power, it will quickly degrade the LEDs and may cause heat issues. Listed on the specs of the LED is the actual power consumption used while running. This is the number you use to determine how powerful your light is and for calculating the footprint of your LED.
Interested in LED grow lighting? Check em out!
Fluorescent Grow Lighting
Fluorescent light emits a cool blue light which is ideal for seedlings and cuttings. This lighting is relatively energy efficient and inexpensive making it another popular choice. Fluorescent lights provide a wide angle of light and emit low levels of heat, which is ideal for the first few stages of a plant’s life or for green leaf plants. Due to the low heat and lack of full spectrum, these lights are not good for flowering or fruit producing plants.
When looking into fluorescent grow lighting it is important to understand the different types available. The most common are T5, T8, and T12 and are categorized according to their wattage, shape, and diameter. The T indicates the bulb is tubular shaped, while the number denotes how many eighths of an inch in diameter the bulb is.
Compared to high intensity discharge lighting discussed earlier, fluorescent grow lights are pretty efficient. Fluorescent grow lighting depreciates slowly, with only a 5-10% of initial lumens after 20,000 hours of usage. Because of their efficiency, T5 lights can reasonably be expected to last close to two years.
Interested in fluorescent bulbs? We have those too!
Plasma Grow Lighting
The final type of Hydroponic Grow Lighting to be discussed is the newest form of technology. Plasma grow lighting generates light by exciting sulfur plasma with microwave radiation which emits a beautiful, almost sunlight-like display. Plasma lights are a full spectrum light and are incredibly energy efficient, which make them a great choice. With that being said, until recently this type of hydroponic grow lighting was not cost effective and had few reviews as to their success in the garden lighting industry. Although they seem perfect, they are still quite a large initial expense and work best when paired with LED lighting to ensure maximum plant growth.
Number of Grow Lights and Light Footprint
A handy tool when dealing with grow lights is the ability to calculate how many lights are needed for a given area. To calculate how many lights you need for your space, you need to determine the amount of watts per square footage needed, the square footage of your area, and the footprint of your lights. High intensity discharge lights typically have a higher footprint, meaning their light covers a larger area effectively. For high intensity discharge lights, shoot for around 50W/sq. ft.. This is the optimal, however a minimum of 30W/sq. ft. will work. Keep these numbers in mind.
When it comes to LEDs, the ideal footprint is slightly smaller than what is officially specified for the light. At the cost of a smaller-than-official footprint, LEDs are often lowered closer to plants to get better light penetration. A good tip that most growers use for LEDs is that you need 32 watts of actual power per square foot if you’re growing high-light plants like tomatoes. Low-light plants like lettuce need somewhere between 11 and 18 watts per square foot.
Now what do you do with these numbers? First you determine how much square foot space you have available for your indoor garden. Then you multiply that number by the W/sq.ft. that we mentioned for both HID and LEDs.
45 sq.ft. space * 50W/sq.ft (optimal) = 2250W
The total number of watts your lights should be 2250W. So a couple 1000W fixtures and a 400W fixture would do the trick.
65 sq. ft. space * 32W/sq.ft = 2080W
The total number of watts drawn by your LEDs should be 2080W. This is where we need to remind you: the actual power draw is lower than what the LED is rated for.
You will need to use the actual power draw to determine how many lights are necessary to reach 2080W.
Put away your pitchforks, I acknowledge that this is an extremely simplified way to calculate lighting for an area. Things like PAR and amount of lumens outputted by your lights are much more important for optimizing lighting in an area. However this process will work just fine for most.
Want to stay up-to-date on hydroponic news and gain access to exclusive hydroponic deals for our store? Sign up for our newsletter. We promise we’re not spammy!
Like this post? See factual errors or typos? Feel free to leave a comment. We’d also love if you shared it on your favorite social media platform.