Indoor Growing Lights 101

Updated: May 25, 2020

Indoor lighting is getting more efficient and affordable as technology advances! Today I'm going to get into the different types of lighting and be comparing their efficiencies. This comparative knowledge is from my experience growing with these lights and will not include any specific light measurements or data.

I am not affiliated with any of the companies on this list. I am giving you my honest opinion and the products I have seen these results with.

Important Definitions:

Watt: the energy DRAW of the light from its power source

Intensity: how STRONG the light is or how many photons it is emitting

Usable Light: the spectrum of light that your plants can use for growth

Spectrum: the combination of colors emitting from the light

Efficiency: how usable the light is for your plant compared to how many watts the light draws

Another thing to consider when looking at electricity costs and efficiency is the heat level. You will have to compensate for the temperature outside weather it is hot or cool, which is why for each light I will specify the level of heat output that it has. Low heat, medium heat, and high heat.

LED (Light Emitting Diode) lighting - The quality of LED lights is determined by the parts used to make it. These types of fixtures have extremely high efficiency compared to the rest of the lighting types I discuss here. LEDs have a driver that powers the fixture (like a transformer or ballast but built differently) and different types of diodes that emit the light. Popular fixtures right now for plant growth are SMD and COB. They are both amazing technologies but I prefer the SMD lights because I think they have a better spectrum for the plants and my plants seem happier under them.

--SMD: (Surface Mounted Device) These are circuit boards that have chips (which contain the diodes) mounted to them permanently. The way they are built, these chips have a variety of color/spectrum outputs, making them ideal for plants. They are also very intense and can support plants that need tons of light, and they have a medium heat output. I have a few different types I like including the RAW LEDs and the PRIME LEDs from HTG Supply.

--COB: (Chip on Board) These are usually pods or bars that have groupings of up to nine diodes inside them. These LEDs have a more efficient output and greater cooling capabilities than SMDs, but are not very customizable in spectrum so they are a bit less versatile. They are great for saving on your electric bill but still getting a high intensity light! These lights have a very low heat output and are much cheaper to cool. Here are some good COB lights from HTG Supply.

Here is a link to shop all HTG Supply LEDs! They have a lot of variety and good quality.

T5 Fluorescent lighting - They come in 2 foot and 4 foot lengths and the bulbs are tubes (that are filled with gasses) and about a half inch in diameter. Great for seed starting and getting plant starts growing for cheap. They are also great for a lot of cacti, succulents, and house plants. With enough light for a plant up to 12 inches tall, these lights cover about as much area as the fixture is in size. The 4 foot bulbs are 54 watts each and you can get fixtures with one, two, four, six, or eight bulbs. They have a medium heat output and the lowest amount of usable light emitted, but are also the cheapest to run. So they are efficient for their purposes, but would be a waste of energy if they are placed farther than one foot from the plant. These bulbs should be replaced every year if you run them for twelve months.

These are the fixtures I buy.

The bulbs come in multiple different spectrums; for ideal garden starts I like to mix the regular grow bulbs with the pure par veg bulbs.

T5 LED bulbs - These are bulbs that go in the same fixtures as the 4 foot fluorescent lights I discussed above but are less watts and double the usable light. They have the same plug in but have a straight line of LED diodes inside the tube instead of gasses, and they have a super low heat output. These are only 41 watts and they can grow plants over two foot tall, and they are significantly cooler than regular fluorescent bulbs. They are leaps and bounds more efficient than regular fluorescent bulbs. They also last three years when the fluorescent bulbs only last one. You can use these lights on any plants that like a medium to high amount of light! I have seen a lot of plants grown under these bulbs that put out a lot of flowers! I have flowered snapdragons, citronella, begonias, Mimosa pudica, Sedum plants, jade plants, and many more under these LEDs.

These are the ones I have used.

315 watt CMH (Ceramic Metal Hallide) lighting - These lights are great if you want to grow a plant to maturity indoors and even get a fruit off of it! I have done amazing things with these lights including seeing an aloe plant flower! They have a high amount of light output for their low 315 watt draw, and they are fairly affordable for the intensity of light you are getting. These are the best bang for your buck if you are looking to stay on the cheap side but still get a very efficient light. They are compact and have tons of usable light covering a solid 3-3.5 square feet, depending on how close you keep the light to your plants. They have a medium to high heat level; they are hot in a sealed area but with proper ventilation and circulation they are easily cooled. Here is the fixture that I have used, and I would suggest using this bulb with it because it has the best spectrum and quality build.

HID (High Intensity Discharge) lighting - this light comes in many different versions. 250 watt, 400 watt, 600 watt, 1000 watt, and more. They come in different spectrums as well including HPS (high pressure sodium, which has a yellowish light), MH (metal hallide, which has a blueish light), and full spectrum. You basically have a ballast that powers a bulb, and the bulb can be put in many different types of hoods to reflect the light downwards. These bulbs work by taking a tube or envelope and filling it with a combination of gasses that, when burned at the right temperature emit a certain spectrum of light. This is also similar to how the CMH lights work, but they are a different type bulb. The ballast and bulb have to match in watts so that the gasses in the bulb burn at the proper temperature to emit the spectrum it needs. People have used these lights to grow plants to flower and fruit for many years. They are used in greenhouses for supplemental lighting as well. I don't use these lights anymore because they have a super high heat level, pull a lot of watts, and have a pretty intense output BUT not a very ideal spectrum compared to the LED and CMH lights that have come out recently. Here is a link to a few of these types of HID fixtures.

Check out this amazing article about PPFD and light intensity if you want to learn more about measuring light and the numbers. We are always evolving to learn more about light; it is something that is difficult for us to pin down simply because photons are so small and light is not easily measured! The knowledge is ever changing and constantly updating, so always keep up on recent research!

I hope you all learned something from this article and if you got this far I appreciate you very much. Email me with any questions or comments to

Happy Indoor Growing (:

Gabby Waterman

Canna Lilly grown under a PRIME LED from AgroMax
Snapdragons grown under LED T5 lights

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