Choosing the best lighting for your facility is essential to growing healthy plants and getting a maximum return from your investment

 One of the most challenging issues that growers face when researching horticultural lighting is interpreting and understanding the many terms and metrics that are used to measure and describe the light and systems. When researching about light spectrum and plant lighting efficacy, you have probably come across some of the terms that we explain here:

Plants and humans do not perceive light in the same way

The human eye perceives green light as a bright white light

Plants see and utilise green, blue and red light


Is a unit of luminous flux that relates to the brightness of light visible to the human eye.  Luminous flux is calculated by weighting (multiplying) the spectral distribution and quantity of visible light by values representing human eye sensitivity to specific wavelengths. For this reason, a light source having a high lumen value may not always be suitable for growing plants. Lumens are related to lux in that one lux is one lumen per square meter.


(Photosynthetically Active Radiation) is a region of the light spectrum (400 to 700 nm) that plants utilise for the process of photosynthesis. PAR is not a measurement or metric but defines the range light needed to support photosynthesis.


(μmol) are commonly used to count the number of photons emitted by a horticultural lighting system.


(Photosynthetic Photon Flux) is a measure of the total amount of light or photons within the PAR region that a light source emits each second. The unit used to express PPF is micromoles of photons per second (μmol/s).

PPF is an important metric for calculating how efficient a lamp is at converting electrical energy into photons of PAR.

Note that PPF does not tell you how much of the measured light arrives at the plant canopy. PPF measurements used to describe light sources should be done in specialised light laboratories using appropriate equipment such as light sensors connected to integrating spheres or goniometers. As you are talking with lighting manufacturers, they should be willing to share third-party testing results and certifications.


(Photosynthetic Photon Flux Density) measures light intensity, i.e. the number of photons within PAR (blue, green, red) that falls on the plant and leaf surface each second. The unit used to express PPFD is micromoles of photons per square meter per second (μmol/m2/s). This measurement is done using a specialised instrument called a PAR light meter or a spectrometer to capture and measure photons emitted by a light source. Ensure that instruments are properly calibrated if you are taking measures at your facility.

It is important for growers using LED grow lights to use the right measurement instruments as there are some that are not truly compatible with LEDs and could give a false PAR range.


Efficacy is a term used to describe how efficient a lamp/fixture is at converting power to photons. It is calculated as the photon output per second (μmol/s) divided by the input power (W) giving the efficacy in μmol/J.


(PPE)  is often used to express efficacy. The PPE is calculated by taking the PAR output and dividing by the input power. Note that PPE does not account for far-red photons (or UV photons) which are also of great importance to plants.

Measuring and interpreting the total output of a lamp is a tricky thing. It is important to understand that light follows some simple geometrical rules. The PPFD decreases with the distance from a lamp while the footprint increases, so it is important to consider the size of the illuminated area (light footprint) and how uniform the light distribution is over this area.

You should always request a light plan for your grow facility before purchasing lights.

Many LED lights are not equipped with optics designed to distribute light uniformly.

Measuring the output of lights at a single point can produce false information about its actual output. Therefore, it is advisable to measure light intensity at many points of an illuminated area.

You want to make sure that the lighting manufacturers you are working with are knowledgeable on horticultural lighting and can provide you adequate information about light output, efficacy, spectral quality and uniformity in units that are relevant for plants.  

It is important that you also consider the light requirements or light needs for your specific crop and plant production. You want your lighting solution to deliver photons that are efficiently absorbed by your plants and enable them to grow well and achieve highest quality.







Here is some interesting information from California Lightworks on the differences between a SolarSystem and SolarXtreme Light. 



Spectrum Control

Yes, with SolarSystem Controller (not included)

No, comes with one fixed full spectrum. Not compatible with SolarSystem Controller.



Proprietary CLW COB (chip on board)


5 Years

3 Years


90-277v automatic recognition

110/120v or 220/240v fixed versions available


Commercial, indoor, greenhouse, personal / grow tent

Personal / grow tent

PAR readings 

SolarSystem 550

SolarXtreme 500

PPFD at 12" 



PPFD at 24" 



PPFD at 36" 



UL Listed 




3 channel adjustable spectrum

Full spectrum


Below is a video on the differences

Click here:- Differences between Solarsystem and SolarXtreme