Landscape lighting can have a big impact on the look of a property and the feeling of security that guests and workers feel after dark. Unfortunately, landscape lighting can also entail high maintenance and operating costs. Fortunately, low voltage (12 volts AC) LED lighting is rapidly helping reduce costs and enhance performance.

Why LED?
• Longer lifetimes (up to 40,000 for high quality luminaires) reduces maintenance
• Lower power consumption (25 percent of halogen or less)
• Easier installation, involving much fewer voltage drop limitations

We’ll cover each of these in detail, but first a warning: There are well-engineered and manufactured LED products and poor ones. We have tested the good, the bad and the ugly, and it is important to buy quality. Cutting costs on the up-front purchase of the lights can be an expensive mistake. In landscape lighting in particular, buying cheap luminaires is more expensive in the long run.

Common mistakes
Using an LED MR16 cup bulb in a luminaire designed for a halogen is the most common mistake. Heat will kill the LEDs quickly. If you take any old landscape bullet enclosure and put an LED cup bulb like this one in the fixture, heat will build up and destroy the LEDs or their driver quickly. The reason is you have a watertight and almost airtight enclosure. Air, a poor thermal conductor, surrounds the bulb and after a while, the LED will burn itself out. Many landscaping contractors ask if they can retrofit their expensive specification-grade bullets with LEDs and the answer is “no.” We have pushed LED bulb manufacturers for written warranties in that situation and the reputable ones won’t do it. So what’s the answer?

It’s best to junk the notion of an LED “bulb” in landscape lighting. Buy luminaires that were designed from the “p-n junction” (guts of the LED) all the way out to the surrounding air. We call these “light engines.” They rely on conduction of heat away from the LED, not convection. They get the heat out so the LEDs don’t burn out prematurely, because they are specifically engineered around the LEDs they house.

Other factors
As always, the housing affects lifetime. High quality aluminum housings with powder coating are great for many applications. Near coastal areas with ocean spray, opt for more expensive solid brass housings. You’re only going to get 40,000 hours out of your LED landscape lights if the housing lasts about 11 years or more, assuming 10 hours per night.

The “driver” is the circuitry in the luminaire that converts the 12 volts AC into the DC voltage the LEDs need. High quality LED drivers will accept a wide range of voltages (9 to 15 volts) without damaging the LEDs or affecting light output. This gives helpful installation flexibility. Ask what the operating range (voltage) is. Some drivers accept a wider range than others.

Advantages of LEDs
Let’s get back to the three advantages listed above:
• Longer lifetimes (up to 40,000 for high quality luminaires) reduces maintenance
Halogen bulbs burn out frequently, sometimes every 2,000 hours. At 12 hours per night, that’s only 167 days, which means paid maintenance people spend a lot of time replacing bulbs. A common problem is the outdoor luminaires oxidize and “freeze” shut, so the simple act of changing a bulb may involve ripping out the luminaire and hauling it back to the shop for some mechanical “persuasion” with finely tuned machine tools and good old-fashioned brute force. So a luminaire that lasts 40,000 hours might save your staff a lot of time. I’ve personally thrown away numerous halogen luminaires simply because they couldn’t be opened to replace the bulb.

• Lower power consumption (25 percent of halogen or less)
We often replace 35 watt halogens with 8.5 watt LED luminaires. If you have 100 35-watt halogen up-lights around a small hotel, left on for 12 hours per night, you save 100 x (35-8.5) x 12 hours x 365 days/year = 11,600 Kilowatt-hours per year. At around 20 cents per KWh, that’s a whopping $2,300 saved per year. That helps justify the investment in LED lights. Part of the reason the math works is landscape lights are typically left on many hours per week, unlike some interior lights. This makes LED a natural for landscape lighting of resorts and hotels.

• Easier installation, involving much fewer voltage drop limitations
High quality LED landscape luminaires have internal drivers that accept 9 to 15 volts AC. Some sell a wide range of transformers, many that have taps at 12, 13 and 15 volts output. So when you have a sprawling complex involving a lot of old lines you have some potent tools at your disposal to fight “voltage drop,” which occurs when you make long runs of thin or degraded lines. On numerous occasions during a landscaping retrofit project, we have been able avoid the expense of tearing up and replacing old lines, simply by using high quality LED luminaires, and multi-tap transformers.

With high quality LEDs you have a triple benefit:
• Full brightness all the way down to 9 volts, unlike halogen.
• The ability to accept up to 15 volts without damaging the luminaire. This is important where the 15 volt tap is used to help a far-away luminaire. You may still want to put luminaires near the transformer, in which case the ones at 15 volts have to be able to survive.
• Power reduction of 75 percent or more using LEDs versus halogen dramatically reduces the problem of voltage drop because the way the math works, the load on the circuit contributes heavily to the voltage dropped on the circuit. So just switching to LEDs will pick up the voltage far from the source.

As with any hot technology, it pays to be an informed buyer. There’s good and bad product on the market. Quality LED landscape lighting is expensive, but in most hospitality installations, the savings in installation, maintenance and operating costs more than cover the higher inintial cost of the lights.

Greg Thorson is an electrical engineer and founder of EnvironmentalLights.com, a pure-LED lighting distribution firm. Contact him at GThorson@environmentallights.com.