[h=3]Conclusions
[/h] The most efficient HPS and LED fixtures have equal efficiencies, but the initial capital cost per photon delivered from LED fixtures is five to ten times higher than HPS fixtures. The high capital cost means that the five-year cost of LED fixtures is more than double that of HPS fixtures. If widely spaced benches are a necessary part of a production system, LED fixtures can provide precision delivery of photons and our data indicate that they can be a more cost effective option for supplemental greenhouse lighting.
I have mixed opinions on this study, it was done for greenhouse environment so has little value for an indoor tent grower.
There was also some debate around the par spectrum reference(low light on green algae) used in this study, it doesn't really match what studies made on cannabis, so in my opinion this study only gives some useful insight for greenhouse growing, no more than this.
