" HPS or CMH Grow Lights? - The Difference | Herbal House NZ

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HPS or CMH Grow Lights?

No matter what you’re trying to grow, or what kind of set up you’ve got, finding the right grow lights for the job is a huge part of the process. The most common grow lights on the market are HPS or CMH, and today we’re going to do a cross comparison of each to help you make the right choice for your grow space. 

The difference between HPS and CMH 

First things first, HPS and CMH are both High Intensity Discharge lights. The difference is based on the chemical makeup, which in turn gives off different light spectrums. 

HPS for example, emits a red or orange glow when heated or lit. This coloration is ideal for all stages in the plant’s growth cycle, but is particularly good for achieving the best flowering available. 

A CMH bulb provides a bold blue glow when lit. Again, this light is good for all stages, however is specifically good for the vegetation phase.

Now despite their slight specialisms, you probably aren’t much closer to making a choice between the two. But don’t worry, we’re only just getting started. 

HPS vs CMH intensity

If you’re just starting out on your horticultural journey, it’s worth knowing that lumens equate to stronger plant growth: More lumens equal brighter light and better growth for your plants. That said, more lumens also mean more power to run. 

At Herbal House, we currently sell HPS grow lights in four power options: 250w, 400w, 600w and 1000w, all of which give out of 2100k color temperature. HPS grow lights don’t have the hugest spectrum, they do offer a great light intensity and a potential for power. 

CMH bulbs on the other hand, are only available in one variant; 315w, but this can be doubled up with a 2-bulb reflector to provide a wattage of 630W. In terms of color temperatures however, a CMH bulb can emit 3100k, which is perfect for the flowering stage, or 4200k for vegetation. Combining a 3100k bulb with a 4200k gives you the perfect solution for providing your plants with all they need during the different phases of growth. 

With this in mind, a HPS bulb is more powerful than the CMH. But CMH does offer more variety when it comes to color spectrums.

HPS: The Pros 

Starting off the pros for HPS bulbs is their potential for power. But what other advantages are there to using this type of lighting? 

In terms of lumens, HPS lights can provide a higher number of lumens than CMH. A single 1000w HPS bulb gives as much as 130,000 lumens – that's three times more than a CMH bulb. 

When it comes to creating the perfect grow space set up, HPS bulbs have more flexibility. There are a wide variety of reflectors that work with this type of bulb – but the same can’t be said for CMH. For example, HPS bulbs can be used with air cool tube reflectors, air cool hoods, single or double ended wings. On the flip side, there are only a few reflectors that can be used with a CMH, including our 315w ballast reflector.

Another benefit is that HPS grow lights can be bought in single or double ended options. This can boost light intensity by another 5,000 lumens – ultimately maximizing the grow cycle for your plants. And, whether you choose single or double, HPS bulbs are pretty affordable, with HPS kits providing you with everything you need to create set up your grow space. 

CMH: The Pros 

Although there are plenty of pros for HPS lighting, it’s not all doom and gloom for CMHs. They have their own set of pros, too. 

As we mentioned above, CMH bulbs have a wider spectrum than HPS. They offer better, even coverage for your plants as a result. Their higher color temperature also means these bulbs can provide a number of light spectrums, rather than just the one. CMH can emit blue, red and white lighting so they are great for using throughout the plant life cycle and maximizing the efficiency of your plant’s vegetation stage. 

Another benefit to consider is the amount of heat CMH bulbs emit. This is one of the biggest advantages of a CMH bulb over HPS. As the bulbs generate fewer lumens, they are much cooler to run than even the small HPS options. So, although the bulbs are slightly more expensive, in the warmer months, CMH bulbs could potentially save you money when it comes to cooling systems. 

Final Thoughts 

Both lights have their benefits, so which is the better option? Well, truth be told, both options are pretty great for your grow space, and the decision is really down to personal choice. Do you want more power? If so, HPS lights are the way to go. If you want a wider light spectrum, it’s CMH. But you’ll also need to consider power, running and cooling costs. 

If you need help understanding your options, feel free to get in touch with one of our team!