id say i prefer led overall. the terp profiles will differ for sure because of the different spectrums, which one you like better is up to you.
there is a couple of studys done that show higher total terps under led, but i dont think i have seen one that actually dives into the difference in terp profile ratios between led and hps.
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emdub27 is right a watt is a watt there is no getting away from it.
if we imagine two sealed boxes perfectly insulated so no radiation can escape and we put a 1000w led in one and a 1000w hps in the other and run them for 24 hours then we check the temps in each box they would be the same.
where we can save on power with led is that you dont need to match led to hps watt for watt for the same photon output, 660watt of good led is equal to 1000watt of hps so there is a 33% saving there.
then due to the total lack of IR in led spectrums your canopy temps are cooler than they would be under hps for the same room/air temps allowing you to run your room/air temps a few degrees warmer, so another slight saving in cooling costs.
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You understand that your plants are absorbing and regulating the light energy they receive correct very much like a heat exchanger.
Yes, I know exactly how plants use light energy. But all of the cooling they emit is evaporative. They don’t remove any heat or light energy, they convert it from sensible heat to latent heat. In a sealed room, you’ve got to remove the latent heat somehow.
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I think everyone agrees that a cmh will produce better quality than an hps. The cmh simply has a fuller spectrum. The standard Samsung blue, osram red, bar style leds aren’t quite there on spectrum imo. The individual diode response is very tight and there are less unintentional side effects of ir and uv. When you get in to more expensive stuff where you can tune the spectrum they can be better than hps.
Feeding to the light source is very important. This was previously posted here by @MellowedOut and does a good job of showing how spectrum effects nutrient uptake.
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Heat != Temperature
All energy is not created equal.
Like the person above said. Sit under 1000 watt led. Or sit under a 1000 watt heater. See which creates more thermal energy. Why will UV burn you but white light won’t?
An ice burg create more heat than a cup of coffee.
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Since you have experience in commercial operations and with leds requiring 55% less cooling, why don’t you share the cooling tonnage used on the larger hps and led rooms?
We literally took down luxx de and replaced them fixture for fixture with fohse o6i and cooling needs stayed the same.
Does anyone else here work with non bar style leds? You definitely feel the heat from a fohse o6i or gavita 1930.
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I run gavita 1930’s in my personal room. They’re plenty hot.
Just no radiant heat below the fixture like with a hps bulb.
But the watts are clearly less, so it’s hard for me to say one way or the other definitively
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If your in this industry you know why. My personal grow is 10 lights…
I think some of the confusion is coming from the fact that you are relying on the same HVAC technology. What if I told you an air exchanger/recycler can remediate the heat from your LED’s just as effeciently. In temperate to cold climates you can pretty much eliminate primary heating/cooling and still be able to actually regulate your rooms… (cheap) co2 included… you can literally suck the heat off your fixtures and exhaust or mix your leds heat because all the heat is right at the fixture.
I got a build I’m doing right now, where incorporating geothermal into the equation should offset certain draw backs even further…
The thermal dynamics of a room completely change.
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You mean using an hrv or erv? I’m curious about these…
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Then you’re cooling savings aren’t coming from reduced heat output from a fixture, they are coming from more efficient cooling. You’re comparing apples to oranges.
I can evaporative cool an hps room for much less cost than dx, but that doesn’t mean I’ve reduced the heat load.
I can remote mount led drivers and cool them using fans, but that doesn’t mean I’ve reduced the heat load.
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I’m never going to be able to convince you that all “heat” isn’t the same… And that some “heat” is easier to move than other “heat”. Probably because there is a break down between what heat and temperature are in thermal dynamics. Heat is the exchange of energy. Temperature is wasted thermal energy. Which HPS/MH HAVE FAR MORE. Each Joul can be represented by a thermal unit, however effecency of the transfer is what creates temperature. And that’s ok. Have a great day!
As far as DE HPS goes I found the PL lighting systems NXT-LP and Philips bulb to be a very good setup, PL has been around for what 40 years or so, I also agree with what @Ralf said about stretch etc. For me I found cold dumping a room for about 2 hours lights on is very effective.
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How cold do you go in the cold dump? I’ll try it…
Generally 5 degrees colder then your nighttime temps usually does the trick . As long as your not having big swings in your temps during day and night time and you have control of your room.
Are you running your lights out temp higher than day temp during stretch too?
No running nighttime temps higher then day would be the standard negative Dif. Most room are positive Dif by default higher temps at day cooler at night lights off, cold air dump is simply a positive dif situation with a 2 hour cold period at lights on so say 85 day time temp, 80 nighttime temp, 75 2 hours lights on temp. most stem elongation happens in the first few hours of lights on. this is to try and suppress that.
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I used to run 2 1k hortilux in a tent and now i use 1200 watts led per 4x8 tent and have better yields. Both can grow really dank buds
Yes. But grow rooms aren’t empty boxes, nor perfectly sealed, nor do the lights stay on all the time.
In your hypothetical scenario above, add some mass to the boxes with the lights, like concrete, water, whatever. Then run both lights 12 hours on and off, and compare the temps of the two boxes. The hps box will cool down when the lights go off much more slowly than the led box, because the heat from the hps transfers to the mass of the room more efficiently than does the led.
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yer i hear what your saying, like growing in a granite cave will wick the heat away different to growing in a wood barn.