Indoor growers have never had as much choice for grow light technology as they do today. In addition to the faithful old HPS technology there are competitive newer technologies such as the rapidly maturing LED, and the emerging ceramic metal halide lights which offer something completely new.

The right technology for you depends on your budget, approach to new technology, and the challenges you face in your quest for home grown self-sufficiency. Here is an overview of the main options and latest developments.

HPS Lights for Marijuana

Without doubt HPS is the lowest cost mainstream way to buy yourself an indoor grow light capable of serious bud production. HPS may be cheap to buy but it doesn’t boast the lowest running costs due to the inherent inefficiency of ageing HPS technology. HPS was adapted to work for indoor growing rather than designed specifically for it.

HPS produces a lot of heat, and it uses a lot of energy producing less useful orange and yellow light wavelengths. The heat can be dealt with through extraction, and in hot climates air conditioning can be used to reduce heat to manageable levels. HPS running costs also include regular bulb replacements after three to four cycles.

For a 4x4 ft. grow room a 600W HPS is often recommended as optimum. A 400W HPS is often recommended for a 3x3 ft. grow room. 1000W HPS lights tend to be used only in larger rooms, such as 5x5 ft. or more. However, many growers feel superior performance and better light spread is achieved by swapping 1000W HPS lights for larger numbers of 600W units.

LED Lights for Marijuana

LED is slowly entering the main-stream as component costs reduce in price while LED intensity improves year-on-year. LED has a higher purchase cost than HPS, but the running costs are lower. The LED grow light market is confused by the presence of premium quality suppliers (including some of the US-manufactured grow lights) and the lower quality imports from the far east. Comparing apples with apples is not always easy and the buyer is advised to do their research carefully.

A good quality LED with a 400W power draw can replace a 600W HPS and use 33% less energy than a 600W HPS in a typical 4x4 ft. grow room. In addition, there is less waste heat generated, no bulb replacements and a much more precise light spectrum. Anyone with a 3x3 ft. grow room looking to use LED should be looking for around a 250W power draw from good quality components.

The better quality LED manufacturers use LEDs which convert 40-50% of the electricity into wavelength specific light. Scrutinize specifications carefully, because many of the lower cost imported LED grow lights use cheaper LEDs which convert only 25% (or less) of the electrical energy to light. They may still have the same power draw as a more expensive grow light but they are producing significantly less light than the market leading LED chips.

LED grow lights are also programmable, this allows variable levels of blue and red light to be introduced at varying stages of the grow. Red wavelengths will promote more stretching, blue light will do the opposite. Red is more useful in bloom, blue is more useful in early veg growth.

Many professional growers are seeing the spectral flexibility, reduced running costs and reduced cost-of-ownership as the most compelling reasons to switch to LED. The main objection to LED for home growing has been the high purchase price. But a few quick calculations show that LED grow light technology eventually pays for itself through energy savings after a few grow cycles.

Plasma Lights for Marijuana

Light emitting plasma (LEP or simply ‘plasma’) is a premium priced grow light technology that appeals to those looking for maximum quality. The wavelengths produced by plasma are similar to the sun—full spectrum growing. Plasma enthusiasts will claim that the quality of the smoke is enhanced by the more natural spectrum which includes some of the wavelengths missing in HPS, including UV. Many growers will add a plasma light to complement (rather than replace) the existing lights—it’s a good way of improving the light spectrum available to the plants. But the cost still deters many.

CMH Lights for Marijuana

Ceramic Metal Halide (also known as light emitting ceramic) is an emerging new technology previously used in photographic lighting. Traditional metal halide lighting uses quartz to provide the light source, with CMH a ceramic material is used for the light source which improves both the efficiency and the spectral output of the resulting light. The improved spectral output and efficiency improvement have been attractive to indoor growers and the results are impressive.

CMH, like LED, seems to be a more progressive approach to lighting technology than HPS and offers some benefits. Research and development continues with CMH, and many expect it to be an area which will see further development in areas such as spectral output and power improvements. One of the more common options, a 315W CMH light is well-suited to a 3x3 ft. grow room and will be a good replacement for a 400W HPS.

Impact of new plant genetics

Many home growers have started to grow autoflowering cannabis varieties in the last couple of years. These grow under 20 (or even 24) hours of daily light from seed to harvest in around 70 days. Often, the harvests from an autoflower exceed those from a photoperiod variety grown under the same conditions in the same time period. That’s simply because autoflowers have the advantage of blooming under 20-plus hours of daylight with consequential advantages in biomass for autos compared to a photoperiod variety which has just 12 hours of photosynthesis in bloom.

The result for home growers is that the grow light is often running for 20 or 24 hours per day instead of 12. This allows heavier harvests in shorter timescales, something all home growers love. But the trade-off is higher electricity costs. That’s another factor accelerating the adoption of high efficiency lighting such as LED.

Commercial vs. Home grower

One of the biggest fixed costs for commercial cannabis cultivators is the electrical costs for running dozens of 600W HPS fixtures. A number of commercial growers have started swapping out their 600W HPS lights for good quality (300W-400W) LED replacements. The reduced electricity costs mean that the payback on the LED lights can be achieved within a couple of years. Many expect the trend away from HPS towards LED will continue, but that is expected to be an evolution rather than a revolution simply because of the upfront costs to upgrade.

The self-sufficient home grower is often operating to a different set of parameters. Quality rather than efficiency is frequently the main motivator. Many home growers regard their growroom as one area of their life where compromise is not necessary. For the enthusiastic hobby grower cost is sometimes no obstacle to the onward and upward improvements to their grow room. And that quest for continued performance and better quality cannabis, both for commercial and domestic production, will ensure continued investment and advancement in grow room lighting technology for years to come.