How to Install Low-Voltage Landscape Lighting

Electrical Know-How: Unlike standard household lighting, low-voltage landscape systems operate on safe, stepped-down power from a transformer — so no electrical experience or permits are required. However, as This Old House electricians have demonstrated on numerous projects, the quality of your wire connections is what separates a system that lasts from one that fails. Take extra care with waterproof connectors at every junction to protect against moisture and corrosion underground.

In this video, This Old House landscape contractor Roger Cook and Mark Piantedosi install landscape lighting for a front walkway.

Steps:

1. Mount the 120-volt transformer to the house wall, preferably behind a shrub to make the transformer less noticeable.
2. Stretch the low-voltage cable from the transformer to each light fixture.
3. Install a ground stake onto the stem (shaft) of each light fixture.
4. Strip the ends of the cable and fixture wires, then twist them together to make two connections.
5. Slide brass connectors over each wire connection, then tighten the connector with a hex-key wrench.
6. To ensure watertight connections, slip heat-treated tubing over the brass connectors, then use a propane torch to seal the tubing.
7. Push the sealed wire connections up into the hollow stem of the light fixture.
8. Firmly push the light fixture’s stake deep into the ground.
9. Use square-blade shovel to cut a narrow trench from one light fixture to the next.
10. Leave an extra 2 feet of cable at each fixture. Push the cable down into the trench.
11. Install lamps (light bulbs) into each fixture and attach the shades.
12. Connect the cable to the terminals inside the transformer, then screw the faceplate onto the transformer.
13. Plug the transformer into a 120-volt receptacle.
14. Flip on the switch and check to ensure that each fixture lights up.

Transformer Sizing: To determine the watt-capacity of your transformer, add up the total wattage of all the lights you plan to install and multiply by 1.25. This gives you headroom to add a fixture or two later without overloading the system. Also, make sure the transformer is plugged into a GFCI-protected outdoor receptacle — if you don’t already have one, hire a licensed electrician to install it.

Cable Gauge Guide: Use 14-gauge cable for lighting systems that total 200 watts or less and 12-gauge cable for systems that are more than 200 watts. Place the first fixture at least 10 feet from the transformer, and space pathway fixtures about 8 to 10 feet apart for even illumination.

Trench Depth Matters: When burying the cable, don’t set it more than 3 inches deep or you’ll have difficulty connecting the light fixtures later. Leave the cable sticking up out of the soil near each fixture point, and if working with sod, make a slit where the fixture will sit and fold the sod back over the soil.

Tools: