How to Install Low Voltage Deck Lighting

Deck lighting is a great way to make your deck more attractive and useful. Follow our step-by-step instructions to learn how to install low-voltage lights. Deck lighting is a great project because low-voltage lighting doesn't usually require hiring an electrician. Installing deck lighting is similar to installing landscape lights. 

You can choose from a variety of light posts, rail lights and stair riser lights. Most deck lighting systems are powered by a 12-volt transformer that is plugged into an ordinary wall outlet. Solar lights that are self-powered are available, and they don't require wiring or transformers. Always read the manufacturer's installation instructions and contact your local building department before starting the project.

Using Transformers for Low Voltage Lighting

Most deck lighting systems require a transformer as a powersource that converts 110-volt line voltage to 12-volt low-voltage electricity. The transformer will plug into a standard outlet and run wiring through a loop to each light fixture. Some transformers use a timer or light sensor to automatically turn the lights on at night. It is very important to purchase the correct transformer for your lighting system. Most LED lights require 12-volt DC volt transformers while most incandescent lights require 12-volt AC transformers. Check the specifications on the light fixtures before purchasing your transformer. 

To determine the needed size of the transformer, you will need to multiply the number of lights by the number of watts and add 10 percent for line loss. 

You will need to purchase a transformer that can supply at least 220 watts. Round this number up to the next available transformer size.

Deck Lighting Wiring Diagram

It is important to use the correct type of wiring for your low-voltage deck lighting system. Most LED lights use 18/2 gauge wire, while most incandescent lights use 12/2 gauge wire. You will need to match the polarity of the wire to the lights. Most wires are split into a smooth black wire and another wire with white lettering or ribbing. You must connect the matching wires to create a working connection. 

You will need to create a circuit by connecting your lights with wire in a routered cavity in the railing or under the deck to protect them and hide them from view. Aurora pigtail wires can be used to connect side-mounted rail lights to the main cable line. Voltage drop can occur from line loss over a long line of lights. The position of your transformer and lights layout will create a low-voltage circuit. For best results, we recommend that you install your lights in a looped circuit. A straight line, T and split load installation can be used for alternate circuit layouts. LED lights must be wired in parallel, not in a series, and polarity must be maintained throughout the lighting system.


Safety first.
Safety first.

1. Using a table saw, cut a 3/8" x 3/8" channel down the center of the top surface of the top rail.


Creating a space to hide the wiring.
Creating a space to hide the wiring.

2. After making your two outside cuts for the channel, move the fence closer to the blade to remove the center material.


Use a ruler and pencil.
Use a ruler and pencil.

3. Mark the center of the top surface on each 4x4 rail post.


We sell this forstner bit.
We sell this forstner bit.

4. Drill a 5"-deep hole in the center of the top surface of the rail post using a 1-1/2" diameter forstner bit.


Creating an opening.
Creating an opening.

5. Place the drill bit in the top rail channel and drill a 3/8" hole in the side of the 4x4 rail post to the center hole.


Needle Nose Pliers
Needle Nose Pliers

6. Pull your low-voltage wires through the center hole and leave 6" of excess wire above the post.


Next to the house.
Next to the house.

7. Run the low-voltage wire down the side of the end rail post.


Tuck the wires under the deck.
Tuck the wires under the deck.

8. Drill a hole through the deck floor and run your low-voltage wires to the transformer.


Just the right amount of wiring.
Just the right amount of wiring.

9. Strip the wire ends back 3/4" with a wire stripper for connections. Align the wire polarity. The negative side is always marked with white lettering or identifying markings. The positive side is smooth black.


We sell a variety of post cap lights.
We sell a variety of post cap lights.

10. Use a weatherproof wire nut to connect the low-voltage wires to the correct polarity. Screw the post cap light to the side of the post with two screws.


Powered up.
Powered up.

11. Connect the low-voltage wire at the end post to the transformer near an electrical outlet.