MH vs HPS Lights: Which is Better
for an Indoor Grow Op?
If you know anything about grow room light systems, you’re probably aware that high-intensity bulbs are a great choice for delivering high yields. HID bulbs, short for high-intensity discharge, give off a highly intense light that plants crave, especially during the later stages of their development.
HID lights do come with a few disadvantages for growing cannabis indoors, including the fact that they give off a lot of heat. This can make maintaining the proper temperature in your grow room challenging. When hung too close to the canopy, this high heat output can bring stress to the plants and even cause irreversible damage.
As long as you’ve got a good handle on climate control and you have enough ceiling space to hang the fixtures far enough from the plant canopy, chances are you’ll be harvesting high yields with HIDs.
Once you’ve decided that HID lights are the best choice for your grow room, the next step is choosing the type of HID. There are two main high-intensity bulb types to choose from: MH and HPS.
About Metal Halide Lights
First, let’s cover the basics of each of these light types. Metal halide bulbs, MH for short, produces light by an electric arc through a gaseous mixture of vaporized mercury and metal halides. They’re mostly used for general indoor and outdoor lighting purposes, especially for commercial spaces since they’re powerful and bright.
This type of bulb emits a bluish-white light, which is ideal for younger plants in their early stages of development. Plants in the vegetative stage crave bluish light, but as they grow and develop, reddish light is more ideal.
About High Pressure Sodium Lights
The second member of the HID family is the HPS bulb. High pressure sodium (HPS) grow lights operate by using a compact arc tube that contains a mixture of xenon, sodium, and mercury. It’s all very science-y, but here’s the general process of how an HPS works:
The xenon gas gets ionized, then strikes the arc tube when voltage is run through the electrodes. The arc generates heat, then vaporizes the mercury and sodium. As the mercury vapor raises the gas pressure and operating voltage, the sodium vapor produces light when the pressure within the arc tube reaches the right level.
Since each HPS bulb emits a large amount of light, they’re generally used for street lighting and security purposes. They’re also used by growers in the later stages of a grow op, mostly because of their reddish, orange-white light output that flowering plants love.
When is LED a Better Choice?
According to Energy Star, LEDs are taking over, and the government agency says that “LED technology is dynamic compared to other lighting technologies offering a long list of potential features that were never possible before and plenty of benefits beyond energy efficiency and long life.”
The impressive efficiency and long lifespan of LEDs is a big reason why many growers have switched over from HID lights. LED lights are a great choice for a lot of growers, especially for small grow rooms that lack ceiling space or have poor ventilation and can’t handle high-heat lights.
However, HIDs almost always produce bigger marijuana yields. That doesn’t mean they’re always the right choice, but if you can incorporate them into your grow room somehow, definitely try to do it.
So which is best for high yields in your indoor garden? The answer depends, mostly on the stage of plant development. MH bulbs are best for vegetative plants, but once you switch over to flowering (especially late flowering), your cannabis crop will be more successful from HPS.
It will cost you more to buy multiple bulb types for your grow op, but the reality is that it’s the best thing you can do for high yields. A lot of growers suggest that you start out with either LED, fluorescent, or high-intensity MH bulbs and then make the switch to HPS fixtures.
The main thing to remember is that HIDs aren’t ideal for every grow room. In many cases, LED grow lights are the better choice, especially for growers looking for the most energy-efficient solution and for grow rooms that can’t handle lots of heat.