Knowledge Center

PAR, Watts, & Mass PAR – Week 3

PAR, Watts, & Mass PAR - Week 3

If you are familiar with grow light systems, you may have heard of PAR somewhere in the grow light industry. P.A.R stands for Photosynthetic Active Radiation which simply measures how bright a light is to a plant. Just as the Lumen is used to measure light intensity for a human eye, PAR is a great unit for determining exactly what plants see and receive. When dividing a grow light’s PAR by the power exerted from the wall via watts, you end up with simply PAR/Watt.

Have a look at our video. Enjoy.


If you saw last week’s video on Coverage then you probably know that optics can vastly change an LED’s strength by focusing the light, or PAR in this case, to maximize efficiency in a grow area. While this seems pretty straight forward, it can be very misleading and a lot of companies will boast large PAR numbers that are exaggerated or embellished.

While using a strong optic, you may be able to focus the light in the center to reach absurd numbers, however this is at a cost. Just like when you use a magnifying glass to focus the suns rays to set stuff on fire, you lose all of the surrounding power to do so. Using PAR/Watt, instead of just PAR, better illustrates the performance of a grow light. At advanced we take this a step further by measuring multiple squares on a grid. By doing this we will get 16 or more center points to average instead of using 1 single “magnifying glass” hotspot. At AdvancedLED we like to call this averaging “Mass PAR”. Once we have determined the Mass PAR we divide it by the running Watts pulled from the wall. If you take a look at any of our data sheets you will find Mass PAR on every one; giving us and you honest numbers and allowing us to compare our lights with other competitors accurately.

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