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We Replaced T5HO Fluorescent Grow Lights with LED T5HO - Here's What Happened

Home /  Blog /  Horticulture /  We Replaced T5HO Fluorescent Grow Lights with LED T5HO - Here's What Happened
T5HO fluorescent grow lights have been around for some time, and have been a popular option for providing plants and seedlings with sufficient light for indoor growing. Although they generally provide light that's "good enough," advancements in LED technology have been rapidly progressing in recent years and are definitely worth a look.

Dedicated LED grow light fixtures are now commonplace, but with all of the various options, the learning curve can be steep, and researching exactly which fixtures, how many to buy, and where to place them can be a daunting task, not to mention the significant financial investment needed.

Today, we look at an alternative solution that removes just the T5HO fluorescent lamps, and replaces them with an equivalent LED T5HO version. This means keeping the same fixture and setup, and just swapping out bulbs, so you don't have to worry about new light fixtures and installing them.

Why Make the Change to LED?

Fluorescent T5HO lamps are a thinner, higher power version of the ubiquitous T8 fluorescent tube. Their typical 54W power rating provides significantly more light output than their 32W T8 counterparts, and this makes them better suited for grow light applications.

Fluorescent tubes, unfortunately, have numerous downsides. Among the most commonly cited by indoor growers are:

1) Mercury content in lamps pose a health hazard, especially when growing plants for human consumption. A cracked or broken fluorescent lamp could require removing all plants from the grow area, and then performing a thorough cleaning and ventilation before moving the plants back in.

2) High energy consumption, leading to high electricity costs and heat buildup in grow areas. In summer months, this could also mean additional electricity costs for air conditioning and ventilation.

3) Shorter lifetimes of 10,000 hours, requiring more frequent lamp replacements and maintenance costs. LED lamps last up to 50,000 hours, and many manufacturers provide a minimum 3-year warranty.

4) Color rendering and spectrum deficiencies, leading to lower quality growth and yield.

What it Takes to Go LED

Generally, when upgrading to a new LED system, you have two choices: either purchase new fixtures with integrated LEDs, or purchase just the LED lamps and use the existing fluorescent fixtures, commonly known as an LED retrofit.

For growers accustomed to using T5HO fluorescent fixtures, an LED retrofit solution is often the most practical solution. Simply use the same fluorescent fixtures, and replace the fluorescent lamps with a retrofit LED tube lamp, just as you would when a fluorescent lamp goes out.

Although the LED retrofit market has grown rapidly in recent years, LED retrofits for T5HO fixtures are still relatively rare and difficult to find, partially due to the complexity in needing to ensure compatibility with fluorescent ballasts used inside fluorescent fixtures.

A Real World Test

We took a T5HO 4-lamp fixture from Agrobrite, and replaced each of the fluorescent tubes with the T5HO PhotonTube™. Installation of these LED tubes is as easy as replacing a burned out fluorescent lamp - no rewiring or modifications are needed.

As soon as we turned the fixture on, the first thing we noticed is how quickly the lamps turn on and emit their full brightness. Unlike fluorescent lamps, LEDs instantly go to 100% brightness, which isn't a critical feature for growing plants, but is nonetheless a nice feature since you can get an immediate visual sense of how much light you will be getting.

The PhotonTube™ product has a power rating of 30W, which is 40% less than the fluorescent T5HO lamps. We confirmed this using a Kill-A-Watt meter, and sure enough, the entire 4-lamp fixture only drew 114 watts, including the ballast. Compared to a measured power draw of 217 watts with the four fluorescent T5HO lamps, this is a 47% reduction!

Saving energy is great, but what about the actual light output? Not to worry - we've tested all of the photometrics extensively. Below are some photos of the test setup for measurement.

First, we measured the 4-lamp fixture with a set of brand-new T5HO fluorescent tubes. We placed our handheld spectrometer 12" away from the exact center point of the T5HO fixture, and pointed it perpendicular to the fixture. To get a true stable reading, we allowed both the fluorescent and LEDs to operate for 10 minutes prior to taking the measurements.

One thing we immediately noticed while taking these photos was a strong green cast coming from the fluorescent tubes. While it wasn't visible to the naked eye, the green colors were coming in strong through the camera lens.

A close look at the spectrum reveals a strong green spike, centered at around 540 nm. This unevenness in the spectrum is what creates the distortion in the camera sensors, and is certainly not something you see in natural sunlight.

After replacing the fluorescent tubes, we then took the same measurements of the PhotonTube™ T5HO product under the same conditions.

One of the areas Waveform Lighting specializes in is spectrum quality and high CRI lighting. The PhotonTube™ is no exception, and boasts a 95 CRI rating. The spectral plot shows a broad and smooth spectrum, something that resembles natural daylight much more closely.

Below is an overview comparing the key specifications we measured. You can also download the full photometrics for the fluorescent T5HO and PhotonTube™ T5HO.

Power consumption

The superior efficiency of the LEDs used in the PhotonTube™ cannot be disputed. The power consumption is down to about half, meaning your electricity costs are cut in half, and the amount of heat generated is also down to a half. Electricity and cooling costs are some of the biggest cost components in a grow operation - the savings will pay for the investment into LEDs in no time.

For a 4-lamp fixture, you will be reducing your power consumption by approximately 100 watts, which works out to around $65 per year in electricity cost savings. If you're running 10 fixtures, that's a whopping $650 in electricity costs!

(Assumptions: 15 c/kWh, 12 hours use per day).

PPFD

Although running on half the power, the PhotonTube™ provides almost as much PAR, providing an impressive 412 umol/s/m2 at a distance of 12 inches from the fixture. This is only a 9% reduction compared to the fluorescent lamps.

412 umol/s/m2 is more than enough light for even the most light-hungry plants that require direct sunlight.

CCT

The PhotonTube™ emits a warmer, yellower light than the fluorescent lamps, with a 4000K color rating. In our tests, we measured an actual CCT value of 3917K, which is darn close. 4000K is an optimal color temperature for grow lights, because it provides a balanced, neutral spectrum that covers longer wavelengths such as deep red and even near infrared, and works very well as an all-purpose light source for both vegetative growth as well as flowering and fruit production.

If you prefer lighting focused on vegetative or seedling growth, the PhotonTube™ is also available in a 6500K color option in the same configuration.

Color Rendering and Spectrum

Color rendering is where the PhotonTube™ really shines. CRI is traditionally used as a measure of the accuracy of color appearance, but it is a great way to understand whether or not the spectral qualities of a light source match that of natural light.

The CRI level of the PhotonTube™ comes in at an impressive 98/100, which indicates that the light is extremely similar to natural sunlight. The fluorescent tubes came in a 87/100, which is a respectable score for a fluorescent lamp, but the difference in CRI values really explain the superiority of the PhotonTube™ spectrum.

Another metric commonly used as a supplement to CRI is the CRI R9 value. R9 is typically used to characterize the spectral quality with respect to red wavelengths. The R9 value of the fluorescent lamps leave much to be desired at 59/100, compared to the PhotonTube's impressive 96/100. A quick look at the spectral diagram also shows very little red wavelength energy in the fluorescent lamps - almost nothing after a moderately sized orange "spike" at around 610 nm.

Should You Make the Switch?

Our tests show that the LED T5HO outperform the fluorescent lamps in every category, while maintaining the same amount of brightness. While the up-front investment costs of an LED T5HO product is going to be higher, longer lifetimes and lower electricity costs means a much lower total cost of ownership over the long run. Are you ready to make the switch? Try the PhotonTube™ risk-free for 60 days and see the difference for yourself!