How does low-voltage landscape lighting work?

A low-voltage landscape lighting system takes ordinary 120-volt house power, steps it down to about 12 volts at a transformer, and sends that safer, lower voltage through buried cable to each light in the yard. A timer, photocell or app decides when it comes on. Most residential systems work this way, from a few path lights along a walk to dozens of fixtures on trees, walls and steps.

This page explains how the parts fit together so you can plan a design and read a quote. The 120-volt connection that feeds the system is a job for a licensed electrician.

The parts of a system

The transformer. In VOLT's description, the transformer is the 120-volt power supply that converts line voltage down to 12-volt AC current.^[1] It usually hangs on an exterior wall or post near an outdoor outlet. Transformers are rated in watts, and the total wattage of the fixtures sets the size. VOLT recommends never exceeding 80 percent of a transformer's capacity,^[1] and adds that once wire losses are counted, the true optimal working capacity of a transformer is about 70% of the transformer's total capacity.^[2] Kichler likewise suggests a transformer with more capability than your initial needs, so fixtures can be added later.^[7]

Many transformers are "multi-tap," with outputs from 12 up to 15 volts. The extra volts make up for what the cable loses: VOLT's example is that on a long run of 100 feet the 15-volt terminal may be needed to deliver 12 volts to the far fixtures.^[2]

Where the transformer goes matters for safety. VOLT's installation requirements call for it to be plugged into a GFCI circuit, never an extension cord, and mounted vertically with its bottom at least 12 inches above the ground,^[2] and placed at least 30 feet from any water feature.^[4]

The cable. Two-conductor direct-burial cable runs from the transformer out into the yard. Low voltage cable is typically buried at least 6 inches deep, though exact requirements depend on your local electrical code.^[4] Heavier cable carries power farther with less loss, so wire size is chosen from the length of each run and the watts on it.

The connections. Each fixture's lead wire is joined to the cable, often with waterproof wire nuts pre-filled with silicone gel that seals around the wires and blocks ground moisture.^[6] Cable connection points are one of the most common points of failure^[6] in a system, which is why good installers use sealed connectors and keep the number of buried splices down.

The fixtures. Path lights wash light down onto walks and beds, spotlights and floodlights point up at trees and walls, well lights sit flush with the ground, and small hardscape lights tuck under steps and wall caps. Some fixtures take a replaceable bulb; others have the LED built in.

The controls. A plug-in timer, a photocell that switches on at dusk, or a smart controller usually sits inside the transformer cabinet.

How the power reaches each light

There are a few ways to wire a yard. The simplest is a daisy chain, with one cable running from fixture to fixture. A hub layout instead groups fixtures within about a 40-foot circle and runs one wire from the transformer to the center of each group,^[3] with the fixture leads meeting there. When the leads are similar lengths, the fixtures in that group see similar voltage.

Matching voltage used to matter more than it does now: older halogen lamps want 10 to 12 volts, while LEDs tolerate roughly 8 to 15.^[3] Even so, Kichler warns that Voltage drop causes unevenly lit fixtures and premature bulb burnout,^[7] so a designer still balances cable size, run length, fixture wattage and the transformer tap for each run. Our answer on why lights are dim at the end of a run goes through what goes wrong when that balance is off.

Low voltage versus line voltage

Some outdoor lights run on full 120-volt power instead. Those systems are built like any other house circuit: VOLT describes 120-volt cable must be buried 18 inches underground, placed in conduit, and have sealed junction boxes at connection points.^[5] Low-voltage systems avoid most of that, which is why they dominate residential yards, but they still start from a 120-volt outlet.

Permits, licences and digging in Virginia

Virginia's Uniform Statewide Building Code says a permit is not required for wiring and equipment that operates at less than 50 volts,^[8] which covers the 12-volt side of a typical system. The same section adds that that exemption does not excuse the work from the code's other requirements.^[8]

The outlet that feeds the transformer is a different matter. The same section lists installations or alterations involving electric wiring among the work that needs a permit,^[8] and Prince William County lists installing a new electrical circuit, fixture, or receptacle among the jobs that need a permit.^[9] Your own county or city building department sets the details. Virginia defines a tradesman as anyone who does electrical work for the general public for compensation,^[10] so the person you pay to add that outlet needs an electrician's licence. Our answer on whether to hire an electrician for landscape lighting covers who does which part.

Trenching for cable is digging, and under Virginia law no person may begin any excavation without first submitting a locate request to the notification center.^[11] A professional installer builds that wait into the schedule.

When to call a licensed pro

Call a licensed electrician when there is no GFCI-protected outdoor outlet where the transformer needs to go, when an existing outlet trips or looks weathered, or when you want 120-volt fixtures. A landscape lighting professional is worth calling for a design with many fixtures, long runs, trees to uplight or cable that must pass under a walk or driveway. Ask for a written quote that names the transformer size, the cable gauge and footage, the connector type, the fixture models and who handles the outlet, the permit and the utility locate, and check the contractor's licence before you sign.

For prices, see what landscape lighting costs in Virginia. You can also browse landscape lighting on Loclis, find electricians in Blacksburg, or read more electrical answers.

Describe your landscape lighting project and licensed local pros quote it.