Another consideration with cost is that some lights run hotter than others—HIDs, for example—so they may require additional fans or an AC unit to cool down a grow space. Extra equipment means more electricity, also driving up your utility bill.
Other considerations when choosing a cannabis grow light
LEDs also typically run a lot cooler than HIDs, so you may not need extra equipment to cool down your grow space, and one LED can usually be used for both vegetative and flowering growth. Some high-end LEDs allow you to change the spectrum for each growth stage.
Best CFL grow light brands
There are daylight bulbs and warm white bulbs; the former better for vegetative growth, and the latter for flowering.
Typically the “blurple” LEDs don’t produce as well as the LEDs with a wider color spectrum (though not always)
Now that you’ve chosen the number of plants, let’s talk grow light size. You need to decide how much bud you want to yield per plant. That’s key to choosing the perfect size light for your goals.
Before I answer this question, let’s talk about plant numbers. It can be hard to decide the right number of plants to grow. Most home-grow laws limit growers to somewhere between 1-6 plants. While it’s easier to grow only a few plants at a time, more plants result in more strains and often bigger yields at harvest.
Fluorescent lights – CFLs & T5s
2.) What size grow light for a 2×4, 3×3, or 4×4 grow tent? (Metric 0.6mx0.6m or 1mx1m, etc.)
True power draw vs equivalent wattage – Whenever talking about the wattage, pay attention to the “true power draw” (how much electricity is being drawn out of the wall) to estimate the strength of the grow light. Ignore “equivalent” wattages because these are marketing terms without any objective meaning.
I believe 2-4 plants per grow is a great compromise between effort and results for a small-scale home grower. But every grower is different!
Why the confusing labeling? In the 2000s, the most popular grow light was the 600W HPS. When LEDs first came out, they were all labeled as “600w HPS equivalent” even though they used a fraction of that electricity and got a fraction of the yields. It makes sense as a marketing gimmick: doesn’t a “600w equivalent” light sound more powerful than a 100w LED? The practice of non-sensical LED labeling has persisted for over a decade, though it seems to finally be falling out of favor. You don’t need high wattage to get big yields, and growers are starting to realize the power of utilizing objective numbers instead of “equivalents” that are made up by marketing teams.
1.) What’s the best size grow light for X number of plants?
Each grow light is optimized to provide full coverage to a specific amount of space
LEDs – many models and kinds
Example of MH/HPS Setups That Yield 1-5 Ounces/Month
These are actually just two names for the same thing. This type of metal halide bulb uses ceramic as part of the lamp just like an HPS. As a result, CMH bulbs are more efficient than regular MH lights (though still not as efficient as HPS bulbs).
Metal Halide grow lights are generally used for the vegetative stage because they produce a bluish light that vegetative plants love, though this type of light can also be used all the way to harvest.
Note: Some growers may have heard of “Induction” grow lights, which are pretty rare these days but still pop up from time to time. There are two types: “Magnetic Induction” grow lights do okay for growing cannabis but they’re pretty much glorified fluorescent lights. “Plasma Induction” grow lights actually perform pretty poorly at growing cannabis.
Keeping CFLs close results in the best yields and growth
Fluorescents are a great choice for clones, young plants, supplemental lighting and can save you money on electricity in the vegetative stage compared to using high power lights when plants are too young to use it all anyway. They can also be used to flower plants in spaces that are shorter than what’s possible with other grow lights (aka ‘stealth growing’).
1.) Fluorescent Grow Lights
CFL grow lights are the twisty-looking bulbs you can find anywhere you normally buy light bulbs. They produce a great spectrum for growing cannabis and can be used in tiny spaces where no other grow light would fit such as the inside of a cabinet.
There is a larger size MH/HPS grow light available (1000W), but at that size it starts going outside the scope of a “hobbyist” grower as far as ease and yields. In addition to needing a lot of extra cooling which costs electricity, a 1000W HPS grow light is less efficient compared to a 600W grow light (as far as how much light is put out for electricity used). I think most hobbyist growers would be happier with a 600W, or even two 600W lights, over a 1000W