nd fruit production .
PAR Vs. Lumens: Which Is Better?
Despite the existence of overlap in the wavelengths used to calculate lumen and PAR, the relatively higher weighting given to yellow light, to which plants are not particularly sensitive, makes lumen values less useful in the selection of grow lights.
The ideal rating would involve the use of YPF weighted PAR, but even the use of PPF weighted PAR, which considers equally all wavelengths within the photosynthetically active waveband, gives a better estimate of a particular grow light’s impact on plant growth than the lumen value.
This is especially true for the majority of LED plant lights, which are heavy in red and blue spectrum light and do not contain as much yellow and green light.
In summary, both lumen and PAR are useful values for determining light intensity.
A higher lumen light will appear brighter to the human eye, because the weighting of the different wavelengths in determining lumen value for a lamp is based on the sensitivity of the human eye. This means that yellow-green wavelengths are given the highest weighting.
Lumen is great for measuring the light intensity when you are lighting your home, or any other space for humans.
But for an indoor grower, PAR is a better indicator of the effect a grow light will have on the growth of the plant, since higher weighting is given to wavelengths necessary for stimulating growth and for the development of leaves, fruit and flowers.
Choosing a light with higher PAR ratings throughout its coverage area means better growth and higher yield in your indoor garden. The lumen rating of the light does not tell you as much about its effectiveness for plants.
Lumens are for humans; PAR is for plants.
-  “Indoor Crop Production Feeding the Future “, Newbean Capital, Local Roots and Proteus Environmental Technologies, March 2015, https://indoor.ag/white-papers/
-  “https://www.merriam-webster.com/dictionary/lumen“, accessed 31st January, 2017
-  “https://en.wikipedia.org/wiki/Spectral_sensitivity“, accessed 31st January, 2017
-  “http://www.growell.co.uk/blog/2015/03/light-measurement-lumens-lux-par-and-micromoles“, accessed on 31st January, 2017.