Hydroponic Grow Lights

The best hydroponic grow lights for you will depend on a number of factors. These include:

  • Cost of the light (energy cost time X number of hours)
  • The plant environment
  • The stage of growth

Fluorescent and Incandescent grow lights

While they are cheap to buy incandescent bulbs are rather inefficient as hydroponic grow lights.

Incandescent and fluorescent grow lights are fine for low-light plants when you expect limited results. However, the light is low intensity and they produce a low level of lumens per watt and are therefore less efficient than High-Intensity Discharge lights (HID) or Light Emitting Diode (LED) grow lights.

Incandescent lights have a much shorter usable bulb life than high-pressure sodium lights and LED grow lights. They also have approximately six times lower light output per watt of energy consumed than a High-Pressure Sodium (HPS) light.

High-Intensity Discharge Lighting (HID)

High-Intensity Discharge lighting consists of a lamp, reflector and power supply. Manufacturers design these lights to produce a high output of photosynthetically active radiation (PAR) for the amount of power consumed. It is not just the quality of the light but the quantity that is also important and High-intensity discharge lights can produce both.

Commercial growers and some of the world’s premier growers use High-Intensity Discharge lights and produce impressive results that would be impossible with conventional fluorescent and incandescent lamps.

Until recently High-Intensity Discharge lighting for horticulture has not been cost-effective. As a result of new lighting products by manufacturers like Hydrofarm and Sunlight Supply, lighting costs have been significantly reduced making the use of such lights profitable.

High-Intensity Discharge lights cover the PAR spectrum (Photosynthetically Active Radiation). The wavelengths of light most important for photosynthesis to occur are the red and blue light spectrum, red being 600 – 680 nm and blue is 380-380 nm. Scientists consider these wavelengths the most important for photosynthesis and HID lights cover these spectrums well.

There are two types of HID lamps which emit different color spectrums.

Metal Halide (MH) Grow Lamps

Metal halide lamps emit light at the white/blue spectrum. Metal Halide lamps are best used as a primary light source if there are no other light sources and little or no natural sunlight is available. They consume large amounts of energy but produce significant quantities of light.

Advantages of Metal Halide Lamps:

  • Best when there are no other light sources
  • Promotes compact vegetative growth
  • Best for vegetative growth
  • Emit high levels of blue light promoting growth of leafy plants

High-Pressure Sodium (HPS) Grow Lamps

High-pressure sodium grow lights have a long usable bulb life and are a much more efficient means of producing light than standard incandescent grow lights. They emit a yellow/orange spectrum of light and have a yellowish glow. They are good when you use them in combination with other light sources such as weak sunlight during the winter months.

Advantages of High-Pressure Sodium Lamps:

  • Work well with other light sources (natural sunlight etc)
  • Best for flowering/budding stages of growth
  • Ideal for a hydroponic greenhouse or commercial growing application
  • Emit high levels of red light good for flowering and fruiting plants

The Hortilux HPS lamps add an additional 30% blue factor to their spectrum making them more efficient than other HPS lamps for solo use.

You can also buy High-Pressure Sodium to Metal Halide conversion bulbs. These can switch from emitting Metal Halide light during vegetative growth then let you switch back to High-Pressure Sodium for the flowering/budding stage of growth.

LED Lights for Hydroponic Gardens

What are LED Lights?

LED grow lights are the most efficient means of producing light for plant growth. The light produced targets narrow wavelengths required for photosynthesis. Furthermore, most of the energy is not lost in the form of heat like with other grow lights. LED grow lights have the highest PAR value (photosynthetically active radiation) of all grow lights.

The downside of LED grow lights is that they are expensive to buy and while being the most efficient, the cheaper models don’t produce enough lumens to be effective for growing a decent size crop.

LED lights are just small light bulbs that can fit easily into an electrical circuit but unlike ordinary incandescent bulbs, they don’t have a filament that burns out, and they don’t get very hot. Therefore, they last a lot longer. You can also configure lights to emit light at a specific wavelength. This makes them more efficient for growing plants which require light between 400 to 700 nanometers.

Advantages of LED Grow Lights:

  • Produce less heat than other light sources which can damage plant and dry up the hydroponic solution
  • Much longer bulb life than other lamps. Typical lifetimes quoted are 25,000  to  100,000 hours
  • Lower energy costs due to higher efficiency
  • No costly cooling system required unlike Halide Lights which get hot
  • LED grow lights do not contain the harmful mercury-filled bulbs that exist in some other grow lights
  • Powerful LED grow lights have been shown to produce higher yields and vegetative growth

Efficient Means of Producing Light

Thanks to new technology LED grow lights have become the most efficient means of producing artificial light for plant growth. This is because LED grow lights have a high photosynthetic photon flux (area) density for every Watt consumed. What does this mean?

Photosynthetically Active Radiation

hydroponic grow light -- plant light spectrum

According to Wikipedia “Photosynthetically active radiation, often abbreviated PAR, designates the spectral range (wave band) of solar radiation from 400 to 700 nanometers(nm) that photosynthetic organisms are able to use in the process of photosynthesis”.

Photosynthetic Photon Flux Density (PPFD) refers to the photosynthetically active radiation emitted per square meter per second. In other words, it is the energy suitable for plant growth emitted every second for every square meter of the plant.

The higher the PPFD the higher the crop yield as the light can cover a larger area.

Plants only require light energy within a narrow frequency of between 400 and 700 nanometers (nm’s) and other frequencies can even be harmful to a plant. A frequency too high can damage the cells and a frequency too low won’t penetrate the plant.

Because hydroponic LED grow lights can be manufactured to emit light at narrow wavelengths specifically suited to plant growth they are more efficient and don’t require as many watts to run as other grow lights.

How to Measure Hydroponic Grow Light Efficiency

The efficiency of a LED grow-light is determined by PPFD per watt of energy. The PPFD per watt will determine how efficient a light source is at producing photosynthetic active radiation per watt of power.

The efficiency of an LED grow light can be expressed as the number of grams of crop produced per watt. However, this will vary depending on the plant and other environmental factors.

Since the photosynthetically active radiation range occurs within the visible spectrum it is common for the brightness of the light to be measured in lumens or lux.

If these lights are left on 24 hours a day and use a high wattage they can still run up your energy costs. You want a powerful LED grow-light that produces a high plant yield but efficient enough that it consumes relatively low wattage.

Hydroponic Guide Sections

To learn more about other aspects of hydroponic gardening, see the following sections of our guide.