WTF Is CDM?
You know when you see something and it's soooo good but doesn't seem to make much sense? That's how some growers feel about CDM, is this shit for real? 315 watts? That's not even going to touch the sides in my grow room! Why should I switch my lights over? HPS is going fine for me! That's just some things we hear from our customers in our shops, if you feel like this, then read on, find out more about CDM lighting and what it is and you might work out that this lighting setup could be the one for you.
WHAT IS CDM?
CDM stands for Ceramic Discharge Metal-Halide, its a design variant taken from the traditional Metal-Halide lamps that use quartz, which in itself was another take on the old favourite HPS (High-Pressure-Sodium). Instead of quartz, CDM lamps use Ceramic arc tubes that can withstand much higher temperatures increasing lamp efficiency, stability and performance. Meaning that CDM bulbs last a lot longer than the usual HPS bulb.
The best thing about CDM lighting is that they pull one fifth less than conventional lamps but still pump out the same level of light output and maintain colour stability.
HOW CAN A 315W LAMP COMPARE TO A 600W HPS?
So, with CDM bulbs, they need loads less power than HPS bulbs to provide a similar level of light output due the technologies involved in each lamp. A standard 315w CDM bulb is comparable to a 600w HPS. Crazy right? you'd think that more power, more crop? Not in this case.
Agricultural lamps are designed to work within the PAR (Photosynthetically Active Radiation) range of the light spectrum, this is the part that is beneficial and usable by all plants to veg. and flower. With that, all bulbs will have a PAR output rating, which in the old days did mean that more power to your lamp the bigger and heavier yields you'd get. Now with changes in technology and advanced manufacturing methods you can in fact get a lamp that has nearly half the power rating and still have the same PAR output (or in some cases, better) as a 600w HPS lamp; cue the 315w CDM bulb.
CDM BULBS ARE EXPENSIVE (APPARENTLY)
If this was true and not some massive marketing ploy thought up by big companies, why isn't everyone using them? Purely because they are expensive, a good 315w CDM lamp like one of these costs nearly 4x the price of a good quality 600w HPS bulb like this. As CDM bulbs are more specialised, you'd need to buy a vegging bulb and a flowering bulb that have a tailored spectrum to those two cycles, whereas the HPS lamp, you can use from start to finish without any issues at all (provided its a dual spectrum of course). Not to mention, that you'd need a specialised ballast and lamp holder for your CDM bulb which would also be more expensive than a basic 600w light kit.
BUT! and it's a massive but....(there's a few actually)
1. The power drawn for a CDM bulb is nearly half that of a HPS, which equates to the simple fact that they are almost 50% cheaper to run, saving you loads on energy costs per grow. Already, not looking so expensive anymore.
2. CDM bulbs last longer than HPS lamps, thats a fact, not marketing, without any PAR depreciation. Around 4x longer actually, where we'd recommend changing your HPS lamp after every grow to maintain consistent results, with CDM you don't need to do this. You'll get about a years worth of efficient performance from your set of lamps.
3. They don't run as hot, because they're drawing less energy to begin with, CDM bulbs stay cooler than HPS lamps. Making it easier on your fans and prolonging the life your filters for the simple fact that they're not having to work so hard on getting rid of excess heat in your grow room. This is more noticeable if you have a fan speed controller attached to your extraction and you'd see a drop in your energy bills too because your ventilation system is pulling less power.
When you add up all these savings in other areas of your grow, using CDM lamps works out to be a much more cost effective option in the long term even though the initial outlay is dramatically higher.
WHAT ABOUT LEDS?
If I was all about energy efficiency I'd choose LEDs surely? I hear you ask; and yes you could decide to go down the LED route, their technology has surpassed itself 10 times over the past 5 years and are more energy efficient than any other agricultural lighting. But are a totally different beast to get your head around, CDM lighting sort of sits in between LED and HPS and for those growers used to the idiosyncrasies of growing with HPS lamps will find that switching over to a CDM setup won't damage their take home crop weight.
If you are interested in CDM lighting and what it can do for you, you can visit one of our stores where we have a full range of CDM lighting setups on display for you to get to grips with and take home if you fall madly in love with it.