How to Put in Low-Voltage Landscape Lighting

Some landscape lighting systems operate on “line voltage,” the 120-volt current from your house. For DIY installation, though, we highly recommend low-voltage systems that operate on just 12 volts. They’re less expensive, easier to install, safer, and use less energy.

Key Components

There are dozens of low-voltage lighting fixtures and accessories available in a variety of styles, sizes, colors, and finishes. Nearly every system, regardless of its complexity, is composed of four basic parts.

Transformer: The power behind every low-voltage system is the transformer. It plugs into a GFCI-protected outdoor electrical outlet and steps down the house current from 120 volts to 12 volts. Most transformers are equipped with a 24-hour timer that allows users to decide when the lights go on and off automatically.

Transformers are rated according to the maximum wattage output. Models range from about 44 watts to 900 watts. To determine which size transformer you need, simply add up the wattage of all the lights in the system. For example, if you plan to string together 10 18-watt light fixtures, then you’ll need a transformer with a wattage output of at least 180.

Low-Voltage Electrical Cable: The cable used for landscape lighting is specifically made for burial underground. It runs from the transformer to each light fixture in the system. Low-voltage cable is commonly available in 12-, 14-, and 16-gauge. The lower the number, the thicker the wire and the greater its capacity.

Which cable to use depends largely on the size of the transformer and the length of cable you need. For example, a 300-watt transformer can power 100 feet of 16-gauge cable, or 150 feet of 14-gauge cable, or 200 feet of 12-gauge cable. Check with the lighting manufacturer to determine the proper-size cable to use for your specific system.

Pathway Lights: Designed for installation along walkways and driveways, this type of fixture represents the most stylish and elegant of landscape lights. Shiny copper or plated-metal fixtures stand out, while green-, black- or brown-painted fixtures can blend in with the surroundings.

Accent Fixtures: The unsung heroes of any landscape lighting design are the accent lights. These specialty fixtures, which are often hidden from view, include floodlights, spotlights, up lights, and wall-wash fixtures. They’re used to shine a light on trees, shrubs, walls, flower beds, fences, ponds, and other landscape features.

Installation Tips

Putting in a typical low-voltage lighting system requires three major steps: laying the cable, installing the transformer, and connecting the lights.

Laying the Cable: Start by laying the light fixtures on the ground where you intend to install them. Space the fixtures 8 to 10 feet apart. Next, unroll the spool of low-voltage electrical cable and lay the cable beside the fixtures. If you come to an obstacle, such as a boulder, tree, or fence, string the cable under or around it.

Now use a square-blade shovel to cut a 2- to 3-inch-deep trench along the line where you want the light fixtures. The trench doesn’t have to be perfectly straight, so if you hit a rock or root, just go around it. You don’t even need to remove any dirt from the trench. Simply stomp the shovel into the ground and pull the handle back and forth to open a deep V-shaped trench.

Set the cable into the trench and push it all the way down to the bottom using a short, narrow piece of 1/2-inch-thick plywood. Don’t use the shovel or other tool; you might accidentally slice into the cable.

Installing the Transformer: Low-voltage cable consists of two insulated stranded-copper wires stuck together. Peel them apart so you have about 4 inches free for each wire. Then use wire strippers to remove about 5/8 inch of insulation from each side. Slide the wires through the retaining strap on the back of the transformer and then insert one wire under the A screw terminal, and the other wire under the B screw terminal. Tighten the screws to secure the wires.

Next, drive a pressure-treated 2 x 6 stake into the ground next to an outdoor electrical outlet. Attach the transformer to the stake with galvanized or stainless-steel screws. Secure the cable to the stake with insulated cable staples.

Connect the Lights Attach a plastic “while-in-use” cover to the outdoor electrical outlet. This type of cover protects the outlet from rain and snow but allows easy access.

Plug the transformer’s power cord into the outlet. Next, connect each light fixture to the cable. Most landscape lighting fixtures come prewired with easy-to-use snap-on connectors. Simply pinch the connector onto the cable. Sharp prongs inside the connectors pierce the cable and make contact with the wires. Since the transformer is already plugged in, the fixture should light up. If it doesn’t, pull apart the connector and try again, or check the lightbulb.

Once you’ve connected the cable, stand up the light fixture and press its pointed stake deep into the ground. Be careful not to hit the buried cable. Check to make sure the fixture is straight, then move on to the next. Once all the fixtures are installed, fill in the narrow cable trench with topsoil and top with grass seed.