Landscape Lighting Wire: Low Voltage and Line Voltage Systems
The wire you need for landscape lighting depends entirely on whether your system runs at 12 volts (low voltage) or 120 volts (line voltage). These two system types use completely different wire specifications, installation depths, and connection methods. Buying the wrong wire for your system type is one of the most common landscape lighting installation mistakes. Here is a clear guide to both system types and their wire requirements.
Low-Voltage Landscape Lighting (12-Volt Systems)
The vast majority of residential landscape lighting systems are low-voltage systems operating at 12 volts DC or AC through a step-down transformer. The transformer plugs into a standard GFCI outdoor outlet (120 volts) and outputs 12 volts to power the landscape fixtures. Because the output voltage is only 12 volts, contact with the wiring presents minimal shock risk, and the installation requirements are significantly simpler than line-voltage systems.
Low-Voltage Landscape Wire
Low-voltage landscape lighting uses dedicated 12-volt direct burial wire sold specifically for landscape lighting applications. The most common size is 12 AWG two-conductor direct burial wire, rated for direct burial without conduit at a minimum depth of 6 inches (much shallower than the 24 inches required for line-voltage UF-B). This wire is not standard NM-B, UF-B, or THHN: it is a specialized cable with two conductors (positive and negative) in a single weatherproof jacket designed for 12-volt landscape applications. Standard residential wire types are not rated or appropriate for 12-volt landscape systems.
Wire Gauge for Low-Voltage Systems
The length of the wire run from the transformer to the furthest fixture determines the wire gauge. Low-voltage systems suffer from voltage drop over long runs because the operating voltage is so low (12 volts). A 10 percent drop (1.2 volts) represents a significant portion of the available voltage and causes fixtures to appear dim or fail to reach full brightness. For runs under 100 feet, 16 AWG or 14 AWG landscape wire is typically adequate. For runs of 100 to 150 feet, use 12 AWG. For runs exceeding 150 feet, use 10 AWG or consider daisy-chaining a second transformer closer to the distant fixtures rather than trying to power them from a long thin wire run.
Line-Voltage Landscape Lighting (120-Volt Systems)
Some landscape lighting applications use standard 120-volt fixtures, including in-ground path lights on dedicated circuits, step lights wired into house lighting circuits, tree uplights on permanent dedicated circuits, and security floodlights on motion-sensor circuits. These fixtures receive full line voltage and require the same wiring standards as any other outdoor 120-volt circuit.
Line-Voltage Landscape Wire: 12/2 UF-B
Any 120-volt circuit running underground to landscape fixtures uses 12/2 UF-B rated for direct burial. The minimum burial depth for UF-B is 24 inches per the NEC. The circuit originates at the panel (or a dedicated outdoor circuit breaker), runs underground in UF-B to the fixture locations, and connects to weatherproof outdoor fixture boxes at each light location. All 120-volt landscape outlets and fixtures located within 6 feet of a pool, spa, or fountain must meet the additional requirements of NEC Article 680.
GFCI Protection for Line-Voltage Landscape Circuits
Line-voltage outdoor landscape circuits require GFCI protection. For outdoor receptacles serving landscape lighting, the GFCI outlet at the circuit origin provides downstream protection for connected fixtures. For hardwired landscape fixtures on a dedicated circuit, a GFCI circuit breaker at the panel is the standard protection method.
Which System Is Right for Your Project?
Low-voltage systems are appropriate for decorative path lights, accent lighting, and general ambiance lighting where the flexibility of a plug-in transformer and simple wire connections is an advantage. Line-voltage systems are appropriate for high-output security lighting, permanently installed step lights and architectural accent lights, and any application requiring the brightness and reliability of full line-voltage fixtures. Many landscape designs use both: low-voltage for path and garden accent lighting, and line-voltage for security and architectural fixtures.
IB Lighting carries 12/2 UF-B for line-voltage landscape lighting projects in standard spool sizes with free freight insurance. Browse our wire and cable selection or call (800) 674-9019 for availability and contractor pricing on landscape project quantities.