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Planning Your Low Voltage Outdoor Landscape Lighting

Planning Your Low Voltage Outdoor Landscape Lighting

A dark yard is a sad place of missed opportunities. Your flower beds, pathways, trees, and even the garden fountain deserve a spotlight. If you’re ready to show off even after the sun has gone down, then some DIY landscape lighting is in your future. Although you can create a system of lights that runs on standard 120 voltage from your house, for a DIY installation it’s recommended that you use a low 12-volt system for safety and cost. Here are the key components, tips, and a few ideas on how to become the best-lit house on the block.

NOTE: Before you dig, or even plan to dig, call the number 811. This will alert the utility companies of your intention to dig so they can come out and mark the approximate location of your underground utility lines. Lines are sometimes buried just a few inches in the ground. A locator should come out within 2-3 working days to mark your property or the area you intend to dig.

Design Your Lighting

innsbruck interior courtyard at night

Whether you decide to use a low voltage lighting kit or buy your pieces individually, you’ll need a plan of action. Ask yourself how you want to light your yard. You can use lighting to highlight your favorite plants and features like statues, trees, or flag poles. Your emphasis could be on safety and use lights to illuminate paths, driveways, and steps. Make sure you also consider lawn maintenance like the chemicals from fertilizer can corrode your fixtures and what happens when you shovel that 5-foot snow drift. Also nothing is more disheartening than taking out a ground fixture with a weed whacker or cutting through your wiring with your lawnmower. 

Lighting Tip: Avoid over lighting an area. Outdoor lights are supposed to accent your yard. Rather than illuminate everything like a sports stadium, think in terms of pools of light and allow features to stand out. Be selective.

Once you take your needs and your rampaging mower into account, you can decide on more practical things like how many fixtures you need and the path the wiring should follow. Here are some types of landscape lights you can use:

Materials Need for Landscape Lighting

12-Volt LED driver

12-Volt LED driver

You also need a transformer or two to step down the 120 Volts coming from your house to 12 Volts for your outdoor fixtures, 100 feet or more of landscape wire, and a square-blade shovel. When choosing a transformer, it’s important to pick one that can handle the total wattage of your fixtures. For example, if you add up the wattages of all your fixtures for a total of 200 Watts then you at least need a transformer with a maximum output of 200 Watts. If you think you might add more lights in the future then choose a transformer with a max wattage that’s 100 to 200 Watts higher than the current total wattage of your fixtures. While LEDs are becoming a more popular choice for this kind of project, if you decide to go with traditional halogen lighting then you will to need buy a transformer with a maximum wattage of 20% more than your total wattage. That means the transformer should never be loaded with more than 80% capacity of its rated max wattage. This is called derating and helps to account for inefficiencies in the transformers. 

Low voltage landscape wiring or electrical cable comes in several numerical gauges or sizes. A lower number means thicker wire and greater capacity to carry the power current for longer distances.  Common wires for landscape lighting are 10-, 12-, 14-, or 16-gauge wires. We recommend 12-gauge or 10-gauge wire for long distances. This is to prevent voltage drop. The further you get from the transformer and its power supply, the more resistance occurs in the circuit which causes the voltage to decrease. 

Lighting Tip: You can run 12-gauge about 100 feet without voltage drop issues as long as the total wattage of the fixtures on the wire is 100 Watts or less.

Total Nominal Wattage
of Transformer:
150W with 16 Gauge Cable 200W with 14 Gauge Cable 300W with 12 Gauge Cable
Max. Cable Length (FT) Max. Cable Length (FT) Max. Cable Length (FT)
88 watts 100 125 150
121 watts 100 125 150
150 watts 100 125 150
200 watts 100 125 150
300 watts not recommended 150 200
500 watts not recommended 150 (2 separate runs) 200 (2 separate runs)
600 watts not recommended 150 (2 separate runs) 200 (2 separate runs)
900 watts not recommended 150 (3 separate runs) 200 (3 separate runs)

Also check that your wire and connectors are listed for direct burial which helps prevent corrosion and other weather-related problems over time.

There are other supplies you might need depending on your design or preferences. Optional materials include:

  • A timer or photocell (if it’s not already built into the transformer)

  • Weatherproof wire nuts (with sealant in them)

  • Weatherproof cover for your GFCI outlet (if your transformer is a plug-in model)

  • Aluminum tent stakes

  • Wire clips and stainless steel screws (for mounting cables to trees)

  • Weather-treated wood post for your transformer

  • Voltmeter

  • PVC pipes, couplers, and caps (to weatherproof connections to path lights)

Last but not least, here are a few more tips to help you in the planning stage:

  • The first fixture should be at least 10 feet from your transformer to prevent it from getting too much voltage and burning out prematurely.

  • To avoid voltage drop, consider running multiple straight runs in several directions, a tee connection run, or a looped run (more about types of wiring layouts in Part 2).

  • Try to center the transformer in your design. It makes it easier to wire the system in cases where you have to split between two or more runs.

  • Path lights should be spaced about 8 to 10 feet apart.

  • Landscape fixtures are also available in LED, which will use far less power than traditional halogen or incandescent lighting.

Remember to take your time and plan your lighting with care. Part two of this how-to will cover the installation of your landscape lighting. If you need more advice call our knowledgeable team of lighting experts at 1-800-624-4488.

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