Shed Wiring Diagram: How to Run Power to a Shed or Outbuilding

Running electrical power to a shed, workshop, or outbuilding is a popular DIY project that dramatically increases the usefulness of the space. Whether you need lights, outlets, or power tools, this guide covers everything from planning to final connections: NEC requirements, underground cable installation, circuit planning, and complete wiring diagrams.

Planning Your Shed Electrical

Determine Your Power Needs

Before digging trenches or buying materials, list what you will power in the shed:

Basic shed (lights and a few outlets):

• 2-4 LED light fixtures (50W total)
• 2-4 duplex outlets for chargers, radio, small tools
• Total load: approximately 500W
• Circuit needed: One 20A circuit (sufficient)

Workshop shed (power tools):

• LED lighting (100W)
• Multiple outlets for power tools
• Air compressor, table saw, or welder
• Total load: 2,000-5,000W
• Circuits needed: Multiple circuits via a subpanel

Heated/cooled shed:

• All of the above plus space heater or mini-split AC
• Total load: 5,000-10,000W+
• Circuits needed: Subpanel with 60-100A service

Single Circuit vs Subpanel

Single circuit (simplest option):

• One 20A circuit from the house panel
• Provides 2,400W at 120V
• Enough for lights and small tool outlets
• Uses one cable from house to shed

Subpanel (recommended for workshops):

• Multiple circuits in the shed on their own breakers
• Can support 240V tools, EV charging, heating/cooling
• Uses a larger feeder cable from house to shed
• More flexible and expandable

NEC Requirements for Outbuilding Wiring

Underground Feeder Cable (NEC 300.5)

Cable from the house to the shed must be buried underground (or run overhead on a pole):

GFCI Protection

All 120V outlets in a detached shed/outbuilding must be GFCI-protected (NEC 210.8).

Grounding

A detached building with a subpanel requires its own grounding electrode (ground rod). The subpanel must have separate neutral and ground bus bars (not bonded).

If running a single circuit (no subpanel), a ground rod may not be required if the circuit has an equipment ground conductor -- but check local code.

Disconnecting Means

If the shed has a subpanel, it must have a disconnecting means (main breaker or disconnect switch) at the shed.

Underground Cable Installation

Option 1: UF-B Cable (Direct Burial)

UF-B (Underground Feeder) cable is rated for direct burial without conduit:

1. Dig a trench 24 inches deep (plus a few inches for the cable bed)
2. Lay 2-3 inches of sand in the bottom of the trench for the cable bed
3. Lay the UF-B cable in the trench -- do not pull or stretch it
4. Lay detectable warning tape 12 inches above the cable
5. Backfill with sand, then native soil
6. At each end (house and shed), transition to conduit using an LB fitting
7. Run conduit up the wall to the panel or junction box

UF-B limitations: It cannot be run inside walls or in conduit for long distances (it is designed for direct burial only). At each building, transition to NM (Romex) or THHN in conduit.

Option 2: Conduit with THWN Wire (Recommended)

Running PVC conduit with individual THWN wires is more versatile and allows future upgrades:

1. Dig a trench 18 inches deep (for Schedule 40 PVC)
2. Lay Schedule 40 PVC conduit in the trench with proper fittings (elbows, couplings)
3. Glue all joints with PVC cement
4. At each end, use a 90-degree sweep to bring the conduit up the wall
5. Pull THWN wires through the conduit
6. Backfill the trench

Advantages of conduit:

• Shallower trench (18 inches vs 24 inches)
• Can upgrade wire gauge later without re-digging
• Protects wire from physical damage
• Can add circuits by pulling additional wires

Conduit Sizing

Wiring Diagram: Single 20A Circuit to Shed

Materials

• UF-B 12/2 with ground (or 12 AWG THWN in conduit)
• 20A GFCI breaker at the house panel (or GFCI outlet in the shed)
• Junction box at each end (or panel at house, first outlet at shed)
• PVC conduit and fittings for wall transitions

Connections

At the house panel:

1. Install a 20A GFCI breaker (or standard breaker + GFCI first outlet in shed)
2. Connect black wire to the breaker
3. Connect white wire to the neutral bus
4. Connect ground to the ground bus

At the shed:

1. Bring the cable into the shed through conduit and an LB fitting
2. Connect to the first outlet (GFCI if not using a GFCI breaker)
3. Daisy-chain additional outlets in parallel
4. Wire lights to a switch from the same circuit

Wiring Diagram: 60A Subpanel to Shed

Materials

• 6 AWG THWN wire (4 conductors: 2 hot, 1 neutral, 1 ground) in conduit
• 60A double-pole breaker at the house panel
• 60A subpanel in the shed (with main breaker as disconnect)
• 8-foot ground rod with #6 ground wire at the shed
• PVC conduit (1 inch minimum)

Connections

At the house panel:

1. Install a 60A double-pole breaker
2. Connect black and red wires to the breaker terminals
3. Connect white wire to the neutral bus
4. Connect green/bare wire to the ground bus

In the trench:

1. Run 1-inch PVC conduit from house to shed (18 inches deep)
2. Pull four 6 AWG THWN wires: black, red, white, green

At the shed subpanel:

1. Connect black and red wires to the main lugs (or main breaker)
2. Connect white wire to the NEUTRAL bus bar
3. Connect green wire to the GROUND bus bar
4. Do NOT bond neutral and ground -- they must be on separate bus bars
5. Drive an 8-foot ground rod outside the shed
6. Run a #6 bare copper wire from the ground rod to the subpanel ground bar

Branch circuits in the shed:

• 20A lighting circuit (14/2 or 12/2 NM)
• 20A outlet circuit (12/2 NM, GFCI-protected)
• 240V circuit for tools if needed

Overhead Power to a Shed

If trenching is not practical, you can run power overhead:

• Minimum height: 10 feet over walkways, 12 feet over driveways, 18 feet over roads
• Use service entrance cable (SE cable) or overhead triplex cable
• Attach to a mast or post at each building
• Drip loops at each attachment point to prevent water entry
• Check local code -- some jurisdictions do not allow overhead residential runs

Common Shed Wiring Mistakes

1. Not deep enough trench: 24 inches for UF-B, 18 inches for conduit. Measure carefully.
2. Using indoor cable underground: NM (Romex) is NOT rated for direct burial. Use UF-B or THWN in conduit.
3. Bonded neutral/ground in subpanel: The subpanel must keep neutral and ground separate.
4. No ground rod: A detached building with a subpanel needs its own grounding electrode.
5. Undersized feeder: Plan for future loads, not just current needs. Run a larger feeder now -- it is much cheaper than re-digging later.
6. No GFCI: All shed outlets need GFCI protection.
7. No permit: Most jurisdictions require a permit for running power to an outbuilding. Get it inspected.

Creating Shed Wiring Diagrams

Plan your shed electrical system with CircuitDiagramMaker. Draw the complete layout from the house panel through the underground run to the shed subpanel and branch circuits. Label wire gauges, burial depths, and GFCI locations. Export as a PDF for your permit application or for reference during installation.

Try the AI circuit generator -- describe "shed subpanel wiring with underground conduit from main panel" and get a complete diagram.

Wire Color Reference for Shed Circuits

Before you connect anything, confirm every conductor color matches its role. Mixing this up is one of the fastest ways to create a dangerous shed circuit.

These colors follow US NEC convention. If you are wiring to BS 7671 (UK/EU) instead, the scheme is different: brown is line, blue is neutral, and green/yellow stripe is earth. Do not mix NEC-colored and BS 7671-colored cable in the same run -- the colors mean different things in each system, and a blue conductor is neutral under NEC but line under BS 7671.

Testing the Circuit Before Energizing

Do not flip the breaker the first time until you have verified the installation with a meter. This catches wiring mistakes before they become a fire, a shock hazard, or a tripped breaker that hides a real fault.

1. Disconnect the circuit at the house panel before touching any connections, and verify with a non-contact voltage tester that the wires are dead.
2. Check continuity on the feeder conductors with a multimeter set to continuity or resistance mode, one wire at a time, to confirm there are no breaks or shorts introduced during the pull.
3. Check for shorts between conductors: with the circuit still disconnected, measure resistance between hot and neutral, hot and ground, and neutral and ground. Each pair should read as an open circuit (no continuity). Continuity where there should be none means a nicked wire or a wiring mistake at a box.
4. Verify polarity at each outlet once the circuit is wired but still off, using continuity checks back to the panel to confirm black lands on hot, white on neutral, and ground on the ground bus.
5. Energize the circuit and test each outlet with a plug-in outlet tester or a voltage tester. A correctly wired outlet reads approximately 120V between hot and neutral, 120V between hot and ground, and 0V between neutral and ground.
6. Trip-test the GFCI using its built-in test button and confirm the outlet (or downstream outlets on the same GFCI) loses power, then resets cleanly.

Troubleshooting Shed Circuit Problems

Conclusion

Running power to a shed transforms it from simple storage into a functional workspace. Whether you choose a single circuit for basic lighting or a full subpanel for workshop use, proper planning, code-compliant installation, and inspection ensure a safe, reliable electrical system that serves you for years.

Plan shed electrical runs with CircuitDiagramMaker -- free online wiring diagram tool with panel, conduit, and grounding symbols.

Frequently asked questions

Do I need a permit to run electricity to a shed?

Most jurisdictions require a permit for any circuit run from a house panel to a detached structure, even a simple 20A run. The inspector checks trench depth, cable type, GFCI protection, and grounding before you backfill. Skipping the permit can void insurance coverage if a wiring-related fire or injury happens later, so check with your local building department before digging.

Can I run shed power through an existing sprinkler or low-voltage conduit?

No. Line-voltage conductors (120V or 240V) must be installed in their own conduit or as direct-burial UF-B cable, separated from low-voltage wiring such as sprinkler valves or landscape lighting. Sharing a conduit risks insulation damage and induced voltage on the low-voltage circuit, and it does not meet NEC separation requirements.

How far can I run a 20A circuit to a shed before voltage drop becomes a problem?

With 12 AWG copper, voltage drop generally stays under 3% up to roughly 100 feet at typical shed loads, but longer runs need larger conductors. Beyond about 100-150 feet, upsizing to 10 AWG or running a subpanel with heavier feeder wire keeps voltage drop low enough that lights and motors run properly.

Is it safe to use an extension cord to power a shed instead of a permanent circuit?

Extension cords are not a code-compliant or safe long-term power source for a shed. They are not rated for burial, degrade with UV and moisture exposure, and lack the fixed overcurrent protection a permanent circuit provides. Use them only for temporary tool power, never as the shed's main supply.

What size breaker do I need for a shed subpanel?

Breaker size depends on the shed's total calculated load, not a fixed number. A basic lighting-and-outlet shed often works fine on a 20A single circuit, while a workshop with power tools typically needs a 60A subpanel, and a heated or heavily equipped shed may need 100A. Size the feeder conductor to match the breaker, such as 6 AWG copper for 60A.

Can I bond neutral and ground in a shed subpanel like I would in a main panel?

No. A detached shed subpanel fed from the house must keep neutral and ground on separate, isolated bus bars, unlike a service-entrance main panel where they are bonded. Bonding them in a subpanel creates a parallel path for neutral current over the equipment ground and grounding electrode, which is a code violation and a shock hazard.

Interactive diagrams for this guide

• Shed Wiring Diagram
• 12x16 Shed Wiring Diagram
• Simple Shed Wiring Diagram

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