Garden & Greenhouse


Understanding Light Movers

Posted June 15th, 2016 by Eric Hopper in ,

lightmoverDo you remember the old riddle, “what goes up, but never comes down”? One answer to this riddle is: your age. However, there is another suitable answer to this riddle: the cost of electricity. As unfortunate as it may be, the reality is that the cost of electricity is constantly increasing. This is just one of the reasons why indoor horticulturists and greenhouse growers using artificial lighting systems need to do everything in their power (no pun intended) to best maximize light energy. Inefficient lighting set ups equate to wasted money and a smaller return on investment. When a gardener decides to implement an artificial lighting system, he or she should take the time to find the most efficient way to utilize that light source. One of the best ways a horticulturist can get the most out of his or her lighting system is to incorporate a light mover.

What is a Light Mover?

It is common for gardeners to confuse light hangers with light movers. A light hanger is a device that allows a horticulturist to make vertical adjustments to the lighting system. In other words, light hangers are the pieces of hardware that allow a gardener to move the lights closer (down) or farther (up) from the plant canopy. Although light hangers play an important role in maximizing the efficiency of an artificial light source, they are not the same as light movers. Light movers are mechanical devices that move an artificial lighting source horizontally over the plant canopy. There are two commonly used types of light movers within the indoor horticulture industry: rail or track movers and circular movers.

Rail or Track Light Movers

The most common type of rail or track light movers are those that have a small motorized “car” that runs the length of the given track or rail. The lighting system is hung from the motorized car and the motor drives its movement. The “car” itself moves the distance of the rail or track (or a section of the rail or track), bringing the lighting system along for the ride. Some rail or track type light movers can be piggy-backed to another, allowing one motor to move two lighting systems simultaneously. This is done by attaching the motorized car to a non-motorized trolley with a rigid rod. The non-motorized trolley has its own section of rail or track. As the motorized car moves on its track or rail, it pushes or pulls the rigid rod attached to the non-motorized trolley which then moves the non-motorized unit. One lighting system is hung directly from the motorized car and the other is hung from the non-motorized trolley. This set up is really handy as it allows a horticulturist to move two lighting systems with one motorized unit. Motorized “car” light mover systems can be set to move any length along the rail or track, as desired by the gardener. For example, a horticulturist may set up the light mover to travel only three feet of the six foot track when the plants are small and then increase the distance the light mover travels as the plants mature.

Another type of rail or track light mover is a chain driven mover. In a chain driven track system, a stationary motor (instead of a motorized car) moves the chain across the length of the track. The chain is the moving part of this system and that is where the lighting system is attached. As the chain is driven back and forth across the length of the rail or track, it moves the lighting system back and forth. Chain driven light movers are designed to move one lighting system only and must travel the entire length of the track. In other words, the length at which they operate cannot be adjusted.

Circular Light Movers

Circular light movers are light movers that resemble a ceiling fan. Put another way, they rotate the lighting system (or systems) by way of a centralized motor. Most circular light movers are equipped to rotate two lighting systems and additional components can be purchased to accommodate up to four lighting systems.

Advantages of Using a Light Mover

The biggest advantage of using a light mover is a more efficient use of the artificial light source. Light movers help to increase efficiency for a few different reasons. First, when compared to a stationary light, a light on a light mover generates less heat; at least in one given area. Although the lighting system on the light rail generates the same amount of heat as a stationary lighting system, it disperses the heat over the entire distance the light system travels. Since this distributes the heat in an indoor garden or greenhouse more evenly, the measures taken for ventilation or cooling will not need to be as strenuous. The next advantage of using a light mover can be connected with the inverse square law. The inverse square law states that the farther the distance from the lighting source, the less light energy there is available. Lighting systems on light movers can be placed closer to the plant canopy since their heat will be evenly distributed throughout the garden. Plants under a light mover system will also grow more evenly because of the more evenly distributed light energy. This is a huge advantage for horticulturists who are continuously rotating their plants in order to achieve uniform growth rates. In an indoor garden, growing plants that are uniform helps use the available light energy more efficiency. Better use of the available light energy always equates to increased yields.

The other unique advantage of using a light mover is that it more closely mimics nature. Indoor horticulture and greenhouse gardening have distinct control advantages over outdoor gardening. However, the overall goal is still to mimic nature. The more effectively a gardener mimics nature, the more beneficial it will be for the plants. In this case, nature is mimicked in the way a light mover places light over a greater surface area of leaves in the garden. In nature, the sun moves throughout the day. As the sun moves, it reaches areas of the plant that were previously shaded. Leaves on the upper section of the plant will create shadows on the lower sections of the plant. In nature, much of this shadowed section would, at some point throughout the day, receive some light. Like the sun, light movers provide light to once shaded areas as they move the light across the garden. Although this is not a direct replication of the sun’s movement, it still increases the surface area of leaves that are receiving light throughout the photoperiod. This mimicking of nature is another distinct advantage of using a light mover in an indoor garden or greenhouse.

Disadvantages of Light Movers

The biggest disadvantage of light movers is the initial cost. Although reasonably priced for what they do, many gardeners are turned off by the initial cost of a light mover system. However, just like other hardware for an indoor garden or greenhouse (fans, ballasts, reflectors, etc.), light movers are part of an investment to make the garden operate as efficiently as possible. Also, when shopping around for a light mover, it is important to remember that not all light movers are made equally. Chain driven light movers tend to be less expensive, but are also noisy and more problematic. Mechanical “car” light movers are the most popular option among indoor horticulturists and greenhouse hobbyists. This is probably due to their reasonable price, durability and adaptability (many can be combined to operate an additional lighting system). The circular light movers tend to be the most expensive option, but could be just the right fit for a large, circular garden space. In the unlikely case that a light mover system breaks down, it is a good idea to have an alarm or high temperature shut off installed. Although this is not likely, it is something to consider with light movers. If a light mover fails during the photoperiod, the plants directly underneath the light source could be damaged by excessive heat.

Aside from cost and the unlikely chance of a break down, the only real disadvantage of a light mover is that the gardener will have to rearrange his or her grow room for retrofitting. This is more of an inconvenience than an actual disadvantage. However, installation is worth mentioning as there are special considerations for light mover systems. For a track or rail system, it is important that the rail or track is level so the motor’s energy is evenly distributed. A twist or incline in the track or rail can wreak havoc on the motor over a long period of time and can cause the system to malfunction. It is also important that the track or rail system is properly anchored to something that can support the weight of both the lighting system and the light mover. That being said, track or rail systems tend to be much lighter in weight than the circular light movers.

In the world of indoor horticulture, light energy is king. Light energy is the absolute driving force behind the final outcome of any indoor garden. For greenhouse gardeners, a supplemental lighting system can increase the overall growing season and in some cases, make year round gardening possible. Considering the high cost of electricity these days, any wasted light energy is wasted money. That is why it is so important for both indoor horticulturists and greenhouse gardeners to do everything they can to maximize the use of artificial lighting systems. Light movers are a simple and affordable way to do just that. Light movers offer horticulturists the opportunity to increase efficiently in their gardens by evenly distributing heat and light while providing the plants with a more natural environment.

Eric Hopper resides in Michigan’s beautiful Upper Peninsula where he enjoys gardening and pursuing sustainability. He is a Garden & Greenhouse contributing editor and may be contacted at

Want More Information? Try These Articles:

Artificial Light for the Greenhouse

Reflection, Diffusion and Cross-Patterns in Horticultural Lighting

Supplemental Lighting for the Greenhouse

Understanding Hydroponic Grow Lights

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