top of page

What is ePAR?

In the world of cultivation lighting, things are ever-changing. Every day, it seems as though manufacturers are improving the ways for us to grow our plants under artificial lighting — and ePAR is the perfect example of that.

If you haven’t heard of ePAR yet, don’t worry! This is a relatively new term that the lighting industry has only recently been exposed to, leaving many of us to have some questions. Specifically, what even is ePAR?

Down below, Luna Cultivation is answering all of your ePAR related questions, from what the term means to how it benefits our plants and everything in between. So, before you get too caught up trying to figure out what this new acronym is talking about, just keep reading.

Defining ePAR

For growers, the term “PAR” is more than familiar. PAR, short for Photosynthetically Active Radiation, is essentially a form of energy that works to further photosynthesis. So, for your plants in your grow facility, PAR is absolutely crucial for their health and wellness.

When determining ideal energy doses for growth and flowering, cultivators have discovered that anywhere between 400 to 700 nanometers falls perfectly within that spectrum. Thus, 400 - 700 nm is considered PAR, plain and simple.

Until recently, 399 or 701 nm didn’t classify as PAR. The PAR energy band was rigidly defined, leaving no wiggle room for photons that fall just out of this range. But, as scientists stay examining this measurement of radiation, they’re discovering that these numbers may be in need of a bit of adjustment. One man in particular, through extensive research, found that these photon’s potential for photosynthesis goes far beyond just those strict numbers.

What We Know Now

After conducting research at the USU’s Department of Plants, Doctor Bruce Bugbee discovered something incredible. By using a combination of LED lights and whole plant testing, the professor found that the plant was capable of undergoing photosynthesis in energy bands ranging from 315-400 and even 700-750. While these bands weren’t incredibly strong on their own, when combined with typical PAR photons, the plants were able to create the chemical energy they needed to survive.

This kind of evidence was remarkable, as it demonstrated that PAR wasn’t just stuck within the confines of 400 - 700 nm. Thus, a new kind of classification became necessary. Now, the lighting cultivation industry has access to something ePAR — Extended Photosynthetically Active Radiation. As the name suggests, this new unit of measurement works beyond the traditional PAR numbers, able to measure radiation readings like we haven’t been able to before.

This extended measurement system may be the key to getting the most out of your yield, truly perfecting the cultivation of your plants. But, how? What kind of effect does this newly defined energy band have on your plant growth, and why would we choose to use it?

Why Use ePAR?

The more we’re better understanding photosynthetically active radiation, the more we’re realizing how out-dated the PAR measurements truly are. While there may not be anything technically wrong with utilizing this system, you just may not be getting the most accurate data from your plants.

Again, because the PAR system has such set numbers, it won’t pick up on anything outside of this realm. But, as we’ve learned, numbers outside this range still do have energy potential for your plants’ photosynthesis and flowering processes. Thus, using an ePAR system allows you to still see the amount of energy your plants are getting and how these numbers are impacting them.

Though ePAR, on its own, may not offer the strongest energy levels available, they still show promise when combined with levels in the typical PAR range. It’s important to remember that different light sources are going to produce different photon levels — some of these levels may fall out of the typical PAR range. If you want to get the best understanding of your light source’s impact, utilizing just PAR measurements simply excludes a lot of potential energy. This, in and of itself, is one of the biggest drawbacks of PAR as a whole, making it incredibly appealing for farmers to move forward with something a bit more advanced.

As it stands, PAR doesn't currently pick up or cover the FR, IR, or UV light regions on the light spectrum. But, UV light plays an incredibly large role in the process of plant photosynthesis, creating quite a big challenge for growers. The idea of the ePAR system, then, is to embrace this bigger picture, understanding that more holistic approaches to cultivation can often be extremely beneficial. We’ll talk a bit more about the connection between EPAR and UV in another article, but we can promise that the relationship there is one that’s worth exploring — despite it being ignored for so many years.

Advancing Your Indoor Lighting Systems

So, there you have it. While the PAR region once defined photosynthesis for plant cultivators, it’s finally agreed that this method is in need of an update. Thus, cultivators are now starting to take a closer look into the new Extended Photosynthetically Active Radiation band, helping to get a better understanding of their plants’ health. Though it may take some getting used to for older cultivators who’ve relied on PAR measurement for so long, it’s clear that the extent of EPAR is far, far more effective.

In general, what we know about EPAR is still a little up in the air. However, the measurement still shows incredible potential, introducing cultivators all across the world to having a closer relationship with your grow. In the lighting cultivation industry, we can expect to see EPAR sensors become more readily available, and more and more farmers hop on the Extended Photosynthetically Active Radiation bandwagon. But, we guess we’ll just have to wait and see!

Still have more questions about plant cultivation?

Luna Cultivation is here to help. As leaders in the world of plant cultivation lighting, we know a thing or two about how to perfect your plant growth. Feel free to contact us personally or check out our blog for even more information.

Recent Posts

See All


bottom of page