Ask Erik

You are asking for a straight-forward answer, so I will do my best to give you a clear and concise response. However, please understand that there are a lot factors that need to be examined about your particular situation and the technologies before a “yay” or “nay” can be given.

Let’s have a look at two different scenarios:
The growing area is in a confined space, such as a closet adjacent to living areas. Moving large amounts of air quickly will pose a problem, for the sake of argument, due to the fact that access to fresh outside air will be difficult. And, there is nowhere to run ducting from an exhaust fan from the growing area to the outdoors or other areas of the dwelling. Even if it were possible to run duct work in this situation, let’s say that it is not desirable to ventilate due to the noise that will be created from moving air through fans rapidly - a common dilemma in urban apartment situations.

Scenario One

In this scenario, you could choose a small wattage HID lamp such as a 250 watt ballast and bulb combo. Yes, you will get very bright and intense light in that small area that correlates to big yields and sometimes high quality. However, this will not be the case in this scenario. The heat generated by the lamp will make the growing area very hot and dry. The plants will be stressed and perform poorly, unable to take advantage of the intense lighting levels. Remember that your plants can only grow as well as the least limiting factor allows. In this case, higher than optimal temperatures will determine the best you can do, which is far below optimal.

Scenario Two

Alternatively, you could choose to use a 90 watt high-output LED grow light that uses one watt or greater diodes in the configuration. These units run extremely cool versus HID counterparts, and use less than half of the electricity. Because the unit runs so cool, and delivers much more exacting light spectrums than the 250 watt HID lamp, plants will not be stressed. Yes, the light levels are not as intense as with the HID, but other growing factors can run optimal such as temperature and CO2 levels. It is easy to increase and maintain higher CO2 levels in LED gardens versus HID gardens. The yield will likely be better than the 250 watt for this situation because while the environment is not as intense, it is closer to optimal than the first scenario due to the fact that excessive temperatures will not be created in the confined area. The plants are also likely to suffer fewer problems such as insects and diseases because they will not be stressed from very hot or dry air.

Now to play the devil’s advocate; if in the same scenario running fans and ductwork were not a problem, or if there was easy access to an air-conditioner, the 250 watt HID would give you a better yield. Because environmental factors such as temperature and good air quality are met near optimal, the increased light intensity available from the 250 watt HID will allow the garden to produce better than with the 90 watt LED, as discussed above. Keep in mind that you are using more than double the electricity to do it. Although plus or minus 100 watts is really not that big an amount of electrical consumption by most standards, if considering it as a percentage difference.

To further muddy the waters, consider that if you replaced the same 250 watt HID with 250 watts of high-output, next generation LED lighting (going watt for watt), you will probably get higher quality and heavier yields with the LED because they are so efficient in converting electricity to usable plant light. Using the same amount of electricity, you can get more plant available light with an LED. Results with LEDs vary with the output of the diodes and with the color combination of diodes. For flowering, results seem to be better with LEDs that have some orange and other spectra incorporated versus standard red and blue only. Keep in mind that high wattage LEDs are considerably more costly to purchase than HIDs, but last at least five times as long.

So in the end, the choice is yours. If there is lots of access to fresh air for air exchanges, the ability to run air-conditioning and lots of space, HIDs will give you big yields consistently, just be prepared for the expense. Running more electricity and investing more money in peripheral equipment such as exhaust and intake fans or air-conditioning are necessities when it comes to high yield HID lit gardens.

With LEDs you spend more on the lights, and spend less on other items, because you don’t need to exhaust or cool the environment nearly as much, also simplifying CO2 supplementation, which can help boost growth rates and yields.

Even if using HIDs for flowering to ensure big harvests, lower wattage LEDs are still great and provide lots of benefits for cuttings, mother plants and vegetative growth to shorter plants, for example, less than 18 inches tall.
Much is known about the quality of HIDs from various manufacturers, as it has become a rather standardized industry. With LEDs, manufacturers range from the good to the bad to the ugly. Check around to see which types and from which manufacturers are working for growers in real world situations, and on what types of plants. For good quality LEDs be prepared to spend some money; many growers have found it to be worth it for certain situations.
So in short, the answer is, it depends on how you want to garden, and what you are looking to get out of it.

Great question; one that will be continued to be debated especially as higher wattage and fuller spectrum LEDs continue to emerge.

Cheers, Erik Biksa