Lighting the landscape with LEDs

The oak tree at the Gov. Thomas Bennett House in downtown Charleston is illuminated by landscape lighting.

The Christmas lights are back in the attic.

Neighborhoods will no longer twinkle red, green and white. As we enter the new year, our landscapes will, once again, become mysteries at night, unless there's a full moon. It doesn't have to stay that way.

Landscape lighting can reveal an entirely new dimension of your property. Low-voltage lighting systems utilize 12 volts to illuminate paths, plants or structures.

For decades, our source of illumination has been Edison's incandescent light bulb in which a tungsten filament would glow when voltage traveled through it. The end result would be light and heat. However, this method is extremely inefficient, converting the majority of voltage into heat rather than light. This was never more evident than in the old Easy-Bake Oven that used an incandescent light bulb to cook brownies. They took forever to make, but it was safe for an aspiring 6-year-old cook.

While fluorescent lights have been much more energy-efficient than incandescent lights, they aren't commonly used in landscape lighting. This may be due to the limitations of bulb shapes or the white light that lacked warmth. Instead, incandescent lights have remained the most common landscape light.

When operating correctly, halogen bulbs produce warm light that does not color shift like standard incandescent bulbs. This is due to halogen gas binding to the tungsten evaporating off the filament that, in a standard incandescent, darkens the inside of the bulb. They still run very hot. In fact, halogen bulbs should not be touched with bare fingers to avoid natural oils from disrupting the uniform distribution of heat.

Because incandescent bulbs have been the standard for so long, most of us have come to associate the amount of light it produces with the number of watts it uses. Watts is a measure of power. The more watts something requires, the more it costs to run. We purchase energy in the form of kilowatt-hours (kWh). For instance, if your kids leave a 1,000-watt light bulb on for one hour, it will use one kWh. And that will cost roughly $0.12.

With halogen lights, we typically use 10-watt light fixtures to illuminate a path or up-light a tree. If the lighting system has 20 lights, each 10 watts, it will require 200 watts to operate. That's still not a significant cost in electricity. At four hours a night, that's about $35 a year. You can do your own calculations at www.citytrf.net/costs_calculator.htm.

However, landscape lighting systems are changing with the development of light-emitting diodes (LED). LEDs convert the majority of voltage into light, wasting very little in heat. They produce more light per watt than halogens. Therefore, the number of watts used by a bulb is no longer an accurate reference to light output. For instance, a 3-watt LED produces about the same light intensity as a 10-watt halogen and lasts almost 10 times as long.

The light quality of an LED, however, was initially stark white. It lacked the halogen warmth. A few years back, Moonlighting Landscape Lighting Systems (www.moonlightinglls.com), a local company that has contributed its expertise to the horticulture program at Trident Technical College for the past couple decades, was hesitant to embrace LED. The fixtures could be unreliable and the light quality wasn't satisfactory. But that has changed. Nowadays, they're getting great results from LEDs with easier maintenance. The light quality, they say, is equivalent to halogens.

Homeowners can expect to change LED bulbs much less frequently than halogens. And for homeowners installing their own system, LEDs are less prone to voltage drop due to wattage consumption that dims lights at the end of long runs. And with fewer watts utilized by LEDs, money can be saved with smaller transformers.

So with all that Christmas money burning a hole in your checking account, consider where lights might fit into your landscape. Not only can they illuminate your pathways, they can inject life into your landscape.



Tony Bertauski is a horticulture instructor at Trident Technical College. To give feedback, email him at tony.bertauski@tridenttech.edu.

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