Grow Lights

Different types of grow lights, clockwise from upper left: high pressure sodium, LED, metal halide, fluorescent tubes, compact fluorescent. 

Welcome to our grow lights summary webpage. 

Admittedly, high intensity discharge lighting (HID lighting) isn't a crucial component of either hydroponics or conventional greenhouse production. Many growers have perfectly functional setups without ever using supplemental lights. However, other hobbyists and market growers rely heavily upon HID lighting at least seasonally, to supplement insufficient natural light due to shading or geographic latitude, and/or to provide an early and/or late growing season boost. Indeed, HID lighting is worthy of at least some consideration even for growers who seem to have sufficient light. If we're going to the length of providing idealized nutrient solutions, growing media and even temperature control, we owe it to ourselves and our crops to at least consider whether our lighting should be optimized as well. This summary page is for anyone who wants to make the most of these lighting supplements. 

Grow lights have come a long way in the last 20 years. Where many of my mentors worked with standard 4' long fluorescent tube fixtures, today's grower has a wide selection of affordable, energy efficient HID lighting options regardless of how much area is under cultivation. The old faithful fluorescents are still in use, but now we also have high pressure sodium, metal halide, LED, and super-bright compact fluorescents. Choosing amongst them all can be a challenge.

Grow Lights Summary Table

We've put together the following grow lights summary table to help you sort out the various options and characteristics of each. This table seeks to provide a quick glance at the various HID lighting options, along with their advantages and disadvantages. For each HID lighting option, we have also written up a dedicated web page describing that option in much greater detail. For those HID lighting options which we have used here, we have included our own experiences and preferences on those detail pages. Click on any of the table hyperlinks to open the corresponding detail page.

Cost Lumens Energy Usage Heat Output Life Span Availability Best Purpose
Fluorescent Tube Low Low High Low Long Common Sprouting
Metal Halide Medium High Low Medium Medium Common Leaf Growth
High Pressure Sodium Medium High Low Medium Medium Common Blossom / Fruit Set
LED High Low Low Low Longest Uncommon Special Purposes
Compact Fluorescents Medium Low Medium Low Short Uncommon Sprouting

This is a lot of information to go through, and it’s taken awhile to compile the grow lights summary table and associated detail pages. If you are in a position of needing to choose between these options, we invite you to take your time, read through all the relevant grow lights pages, and ask lots of questions before making your choice.

Hopefully, either the summary table and/or the detail pages will answer whatever questions you may have about your own plans. We are always on the lookout for new HID lighting options. As those options hit the marketplace and start service, we try to gather either personal and/or peer review comments for how well they do their work. It's an on-going process. 

If you learn about some new form of HID lighting and have not been able to find information on it, let us know and we’ll add it to the list above, with a complete review. If you have already reviewed the HID lighting summary table, and detailed pages, and still have more questions, let us know that too and we’ll try to answer those questions. This website exists to help you with your growing goals. Let us know if there’s any other way we can help you achieve those goals.

Additional Resources

We are not the only folks studying the pro's and con's of various grow lights.  Academic institutions, private companies and non-profit organizations are doing research as well.  We have compiled a list of PDF documents below which will give a tremendous amount of additional information on these various lighting options, including real-world performance.  We hope that this information is as helpful to other readers as it has been to us.
Utah State University offers a detailed cost comparison of grow lights as a free PDF factsheet download.  The factsheet entitled Supplemental greenhouse lighting: Return on Investment for LED and HPS fixtures, discusses HPS, MH and LED lighting in commercial greenhouse production, and examines the cost effectiveness of each.

Cornell University offers a PDF called Evaluating Supplemental Light for your Greenhouse, which was originally published in 2001 by researchers from the University of New Hampshire and Clemson University.  In this six page PDF, the researchers describe the specific jargon used by HID lighting manufacturers, examine the lighting requirements for standard commercial greenhouses, and compare the performance of metal halide and high pressure sodium lamps side by side.  The article pre-dates many of the newer fixtures but it still provides valuable baseline information.

Chena Hot Springs in Alaska recently conducted a study on LED lighting for commercial greenhouse purposes.  The study, called Improved vegetable growth in greenhouses by using tuned LED lights to enhance photosynthesis, was funded in part by the State of Alaska Division of Agriculture, and in cooperation with the University of Fairbanks' Controlled Environment Agricultural Laboratory, llooked at how LED lighting could improve both performance and energy efficiency as compared to either MH or HPS lamps, for both vegetative and fruit development, in year-round production in this harsh arctic climate.  This detailed report was able to show improvements in both categories, but also identified several categories which called for more research.

The University of Arizona's Controlled Environment Agriculture Center published a Powerpoint slide show, (available for download in PDF format) entitled Applications of supplemental LED lighting in vegetable propagation, which examined how LED lighting compared to conventional HID lighting for both commercial fruit and flower production. Their research not only looked at conventional wavelength performance, but also some far-red-shift options via LED, for flowering production.

Educational Materials

In addition to research, a few organizations are coming up with hydroponic lesson plans to demonstrate a variety of biological and physical science principles.  As part of those curricula packages, different forms of lighting are discussed, tested in various growing environments, and evaluated in terms of how light levels, photoperiod, wavelength and other lighting criteria impact plant growth.  Here are two such programs:

AmHydro has put together an educational package, in conjunction with a variety of state educational departments, to demonstrate a variety of scientific, technical and mathematical principles to various age groups.  For example, one such educational package was created for the Washington Association of Agricultural Educators, and is available as a free PDF download.

NASA has developed a comprehensive set of classroom materials, available for download in PDF format, called The Light Plants Need.  This set of lessons, suitable for grades 3-8, leads students through a series of lectures, exercises and experiments to show how different forms and wavelengths of light affect the growth and productivity of plants.  These classroom materials include lesson planning, video links, exercise/experiment suggestions, and a list of materials required or suggested for each lesson.  While the information presented is very basic, it is a good science-based tutorial which uses both LED and fluorescent lighting of different colors to demonstrate photosynthesis.

Always More To Learn About HID Lighting

The above information is just the tip of the iceberg, in terms of the amount of available information.  However, much of the information online is so riddled with unsubstantiated claims, it takes awhile to sort through.  As we continue to gather information on this topic, we'll post the best sources of information here and on the various HID lighting pages.  In this way, we hope growers will be able to get the information they need to make well-informed HID lighting decisions for their operations.  If we have overlooked a report which provides well-researched HID lighting information, please Contact Us with the details and we'll be happy to add it to the list.

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