Indoor Grow Lights, How To Set Them Up?

Indoor Grow Lights, How To Set Them Up?

Lighting is a critical factor of cannabis cultivation

Indoor grow lights? Lighting is a critical factor of cannabis cultivation. For the indoor grower, artificial light poses many challenges. In this blog, we’ll help you position the right grow lamps the correct distance from the canopy, without cooking your marijuana with high temps.


Contemporary indoor cannabis cultivation usually involves at least one of three artificial light sources: HID, CFL, and LED. Frequently, growers use a combination of grow lamps. Of course, there are other, more antiquated lighting technologies, but they are all pretty much “Betamax” lamps. This blog will focus on the most common lighting used by the 21st-century cannabis cultivator. We are going heavy on the practical grow room advice without relying on the pseudo-scientific stats.

HID or high-intensity discharge lamps have been the grow lights of choice for every kind of indoor grower from beginners to pro cultivators since the early 1990’s at least. Over the years, lamps have become more efficient, ballasts have gone digital, and reflectors have gotten bigger and better. Growers that favour HID are big believers that lumens are the only output statistic that matters when it comes to lights.

Sure, CMH or ceramic metal-halide has come on the scene and the 315W CMH bulb is impressive, but a rather expensive upgrade for a standard MH or metal-halide lamp. Moreover, 315W CMH is not quite as high performance as a high-end dual spectrum/agro 600W HPS or high pressure sodium lamp. Similarly, CFL shows some promise, but always runs a distant second to the tried and trusted HID.

LED or light-emitting diode is the up-and-coming breakaway technology that looks to end the reign of HID for cannabis cultivation. The latest generation of LED systems are now capable of producing comparable, and in some cases, superior quality marijuana than the average HID set-up. PAR or photosynthetically active radiation is the metric that LED zealots consider most important.

It’s best not to get too obsessed about the various new measures of light and modified light spectrums. Keep it simple. Think of light in terms of watts and electricity bills. Next is the question, “How much power consumption?” Followed by, “How much heat will the lamp produce and how much light will it emit?”

Indoor Grow Lights


In ordinary decent stoner terms, HID has gotten some new bells and whistles, but the core principles of cultivating cannabis with this kind of artificial light remain the same. MH for vegetative growth and HPS for flowering. Although, the dual spectrum HPS lamps are a popular alternative and probably even better for autoflowering strains.

400W and 600W bulbs are the most suitable for indoor cannabis cultivation. Lights need to be hung level. The optimal light height or OLH is between 30-50cm above the plant canopy. This means carefully fastening the reflector to the ceiling or roof of the grow tent with either easy roll hangers or rope ratchets.

It’s best to use fixtures that can be easily adjusted and repositioned as the plants mature and grow taller. However, seedlings and cuttings may find a 600W MH too intense and a 60cm+ distance overhead might be more appropriate.

Don’t mess with light rails unless you’ve got the engineering credentials. Stationary lights that don’t wobble with a level, horizontal bulb housed in a clean, open reflector is professional, standard cultivation. Ideally, use a large reflector, or as big as will squeeze into the grow space, with a wide spread to utilise the entire area.

Glass filters, light, and air-cooling lamps are expensive. Therefore, cool tubes are really only suitable for closet grows as they have some of the worst reflective properties of any reflector on the market. Adding more lights and more fans means higher power bills.


Generally, 400-600W per m² is plenty of light for a home grow show. Commercial growers may push this to 1000W+ for maximum yield. Packing as many lamps as possible into the grow-op is not a fast track to a heavy harvest. More HID lamps means more light, but also a lot more heat. These babies run hot. 250W lamps are for micro-growers only.

Led Setup Indoor Grow Lights Cannabis Cultivation

The only advantage the 250W lamp offers is that plant tops can get as close as 20cm to the bulb. Heat output is far less than a 600W, but light will not penetrate as far. Limited light will reach the lower branches of taller plants.

The addition of just one extra 600W HPS can massively increase grow-op temps. It’s often a less costly and more effective solution to invest in upgrading the grow room instead. Maybe cover the walls in Mylar or upgrade from a magnetic ballast to a dimmable, digital ballast, or go all the way to LED.


The answer is as many or as few as the grower prefers. You can pack 16 cannabis plants in 11l square containers into a 1m² grow space in a SOG. Alternatively, a grower can fill the same space with one large plant using the ScrOG method.Either way, the yield will be comparable. Again, it’s all about how you make use of the light and the grow area.


CFL or compact fluorescent light is really effective in the cool white spectrum as an alternative to an MH bulb. A 250W CFL can deliver comparable results to a 400W MH lamp. This is achieved by hanging the CFL as close as 10cm above the plant canopy. CFL runs cool and can get really close to plants without burning foliage. Plus, CFL lights will only marginally increase grow-op temps. This makes CFL perfect for seedlings, cuttings, and for use during vegetative growth. CFL lights are sometimes the only option for micro-growers.

Unfortunately, CFL boasts neither impressive lumen nor PAR output figures. Worse, CFL lights are not very effective for flowering marijuana. Cannabis plants need far more intense illumination during bloom than CFL can supply. Expect lightweight yields and loose buds from CFL lights in the flowering phase.

Led Setup Indoor Growing Cannabis Cultivation


The latest LED Grow Lights systems have finally achieved parity with traditional HID lighting systems. At present, the situation is similar to when flat screen televisions first became available at the turn of the century. The benefits and advantages were plain for all to see. However, the limiting factor was prohibitively high prices by the leading manufacturers.

High-performance LED kits that draw 350-400W and can easily outperform a 600W MH and HPS configuration with a full spectrum array can come at competitive prices so it’s worth checking manufacturers like Mars Hydro or Viparspectra and if you’re looking for top of the game models then Black Dog LED or Unit Farm . There are some models that really can do it all. The very best systems can run cool and are incredibly economic in the long-term. Hanging distances vary widely, so buyer beware and make sure to check the manufacturer’s instructions.

LED technology is rumoured to have been reverse engineered from the 1947 Roswell UFO crash, so nobody really understands the tech 100%. We might be growing cannabis with the headlamps from an alien craft. One thing is for certain, as soon as the price drops, LED lights are sure to replace all other artificial lights used for cannabis cultivation. 21st century LED tech allows the grower to pack in more light with less heat and far fewer watts. That’s a game-changer.

Source: Royal Queen Seeds