Running Electricity to a Shed: The Complete Wire Selection Guide
Running power to a detached shed transforms it from a storage box into a fully functional workspace, hobby room, or garden office. The project involves two distinct wiring segments: the underground feed from the house to the shed, and the interior wiring inside the shed itself. Each segment uses different wire types and has its own code requirements. Here is a complete guide to planning and purchasing wire for a shed electrical project.
Planning the Underground Run
The first decision is how much power the shed needs. A basic shed with a few outlets and lights needs only a single 20-amp, 120-volt circuit. A workshop shed with power tools, a compressor, and potentially a welder or EV charger needs multiple circuits and potentially a 240-volt feed. Start by listing every outlet, light, and appliance the shed will have, then calculate the total amperage to size the underground feed correctly.
For a basic shed with one or two circuits totaling under 20 amps, a single 12/2 UF-B cable carries both the hot and neutral conductors for one 120-volt circuit. For a shed with multiple circuits, running two separate 12/2 UF-B cables allows two independent 20-amp, 120-volt circuits. For a shed requiring 240-volt power (welder, large compressor, EV charger), run 10/2 UF-B for a 30-amp 240-volt circuit, or larger gauge UF-B for higher ampacity needs. For sheds requiring significant power (60 amps or more), running THHN conductors in Schedule 40 PVC conduit to a small subpanel in the shed is the standard approach.
Underground Cable Options
12/2 UF-B Direct Burial
UF-B (Underground Feeder cable) is the most common choice for shed power runs. It buries directly in the earth without conduit, requires a minimum depth of 24 inches, and handles the 20-amp residential circuit requirements for most basic shed applications. UF-B is less expensive than conduit installations for simple single or double-circuit runs and requires no conduit fittings or sweeps. The tradeoff is that replacing or adding circuits later requires digging up the cable, which makes conduit the better long-term investment for sheds you plan to use extensively.
THHN in PVC Conduit
Running individual THHN conductors through Schedule 40 PVC conduit requires more upfront installation effort but provides significant advantages. Conduit depth is 12 inches rather than 24 inches, which reduces trenching depth and effort. Future circuit additions only require pulling new conductors through the existing conduit without any digging. Larger conduit (1-inch or larger) can accommodate multiple circuits in a single trench. PVC conduit is non-conductive, does not corrode underground, and is available in sweeping radius elbows that allow gradual bends from underground to above-ground transitions without pulling damage to the conductors.
Shed Entry and Exterior Transition
Where the underground cable or conduit enters the shed, it must transition from the underground installation into the shed wall through a weatherproof entry fitting. For UF-B, use a weatherproof conduit connector and seal the entry point against moisture. For conduit runs, the conduit continues up the exterior shed wall and enters through a weathertight fitting. Inside the shed, the cable or conductors connect to the main disconnect or sub-panel that distributes power to the individual circuits.
NEC Requirement: Disconnect at the Shed
The NEC requires a means of disconnecting power at the shed (a main breaker or disconnect switch). This can be a small subpanel with a main breaker, a standalone disconnect switch, or the first breaker in a small breaker box mounted inside the shed. The disconnect allows the shed power to be shut off at the shed itself without requiring a trip back to the main house panel.
Interior Shed Wiring
Inside the shed, wiring follows standard residential practice. Outlets use 12/2 NM-B on 20-amp circuits with GFCI protection (required for all shed outlets per NEC 210.8). Lighting uses 14/2 NM-B on a 15-amp circuit. In unfinished sheds with exposed framing, use NM-B through bored framing holes or MC cable for exposed surface runs where physical protection is needed. Three-way switching between the shed door and an interior location uses 14/3 NM-B between the two switch points.
Grounding Electrode at the Shed
A detached structure fed from the main house panel requires its own grounding electrode system at the structure. The most common approach is two ground rods (8-foot copper-clad rods) driven at the shed and connected to the neutral bus in the shed subpanel or disconnect. This local grounding electrode limits the magnitude of any ground fault voltage that could develop between the house and shed ground systems.
IB Lighting carries 12/2 UF-B for direct burial shed runs, THHN conductors in all standard gauges for conduit installations, and 12/2 NM-B for interior shed wiring. All wire ships with free freight insurance. Browse our wire and cable selection or call (800) 674-9019 for a complete shed wiring package quote.