Interesting how things work out with the two lights. The PPFD values below are for a 2' x 4' area in the center of the light cast meaning PPFD values for the 500 watt light do not represent the full 3' x 5' area. Undoubtedly, the additional wattage will generate higher readings if the 500 watt light were used in a 2' x 4' tent due to the reflective walls.
In the data below, the 500 watt light will generate about 5% more light but the 320 watt light is more uniform.
View attachment 5212533
This is the text for the above data:
PPFD Values Average StDev ∆% from Center Reading
500 watt 702 868 980 1030 1030 980 868 702 895 119 39% 24% 14% 10% 10% 14% 24% 39%
753 962 1098 1145 1145 1098 962 753 990 142 34% 16% 4% 0% 0% 4% 16% 34%
753 962 1098 1145 1145 1098 962 753 990 142 34% 16% 4% 0% 0% 4% 16% 34%
702 868 980 1030 1030 980 868 702 895 119 39% 24% 14% 10% 10% 14% 24% 39%
Average 728 915 1039 1088 1088 1039 915 728 942
StDev 29 54 68 66 66 68 54 29
320 watt 677 823 928 970 970 925 823 677 849 106 36% 22% 13% 9% 9% 13% 22% 36%
764 915 1015 1061 1061 1015 915 764 939 107 28% 14% 4% 0% 0% 4% 14% 28%
764 915 1015 1061 1061 1015 915 764 939 107 28% 14% 4% 0% 0% 4% 14% 28%
677 823 925 970 970 925 823 677 849 106 36% 22% 13% 9% 9% 13% 22% 36%
Average 721 869 971 1016 1016 970 869 721 894
StDev 50 53 51 53 53 52 53 50
∆ µmols 500 vs 300 25 45 52 60 60 55 45 25 46
-11 47 83 84 84 83 47 -11 51
-11 47 83 84 84 83 47 -11 51
25 45 55 60 60 55 45 25 46
Average 7 46 68 72 72 69 46 7
∆% µmols 500 vs 300 4% 5% 5% 6% 6% 6% 5% 4% 5%
-1% 5% 8% 7% 7% 8% 5% -1% 5%
-1% 5% 8% 7% 7% 8% 5% -1% 5%
4% 5% 6% 6% 6% 6% 5% 4% 5%
Average 1% 5% 7% 7% 7% 7% 5% 1%
Data source:
https://tinyurl.com/2s425x7j
https://tinyurl.com/2mca59t6
The efficiency difference would be that you're running the 500 watt driver at a lower input amperage. I'm not an EE but the "history major" part of my brain tells me that a 500 watt driver at 300 watts, for arguments' sake, will last longer than a 320 watt driver at 300 watts. Having said that, I would expect that the service life of the 320 watt driver is
many years.
Congrats on the new tent.
You won't go wrong with either light. A key factor for going with either light has nothing to do with the fact that it's a Growcraft. Not that I would buy one but one thing in common between Chilled and HLG is that they're among the few manufacturers that sell a veg light and a flower light. That's important because blue light is great for growing plants that are short and compact but it hammers yield. Bugbee talks about this in some of his videos and
it's here in a case study on the Apogee site:
"Through the three different trials, they found that as the percent of blue photons increased from 4 to 20%, flower yield decreased by 12.3%. This means that flower yield increased by 0.77% per 1% decrease in blue photons. However, it is thought that far-red photons also played a small part in the 12% decrease. Additionally, the blue photon fraction had no effect on final cannabinoid concentration."
Growcraft "full cycle" (ie flower) lights have a small percentage of blue in them. I believe that it was in a Bugbee video that some amount of blue was needed in flower to avoid deformed plants however, as cited above, blue light does have the effect of reducing yield. Almost all LED grow lights have significant amounts of blue in their spectrum and that means that growers are losing about ⅛ of their potential yield. Ouch.
