An outbuilding feeder circuit is a permanent installation with requirements a cord across the lawn never triggers: a disconnecting means at the building, a grounding electrode system for that structure, the right wiring method for burial, and separation of grounded and grounding conductors at the remote panel. None of that is optional because the building is small.
Why a cord is the wrong answer even temporarily
Extension cords are listed for temporary use with portable equipment. Running one to a shed to power lights and a freezer turns it into permanent wiring made from a product never intended for it. The cord sits in wet grass, gets driven over, gets damaged where it passes a door, and has no overcurrent protection appropriate to a fixed installation. It also has no equipment grounding integrity you can rely on over time. If the shed needs power permanently, it needs a feeder or a branch circuit installed as fixed wiring, and the difference in cost is smaller than most people assume once the trench is open.
The disconnect at the building
A detached structure supplied by a feeder or branch circuit needs a means of disconnecting all ungrounded conductors, located at the structure. This exists so that someone working in the shed, or a firefighter attending it, can kill power without walking back to the house. For a small building the disconnect is often a small panel with a main breaker, which conveniently also provides the overcurrent protection and the spaces for the local circuits. Where only a single circuit is run, a suitable switch or breaker enclosure serves the purpose. The specific rules about number of disconnects and their location come from the code, so read them rather than improvising.
Grounding at the outbuilding, and the neutral question
A detached structure supplied by a feeder generally requires its own grounding electrode system, connected to the equipment grounding at that building. This is separate from the electrode system at the house. The other half of the arrangement is that at the remote panel, grounded conductors and equipment grounding conductors must be kept separate, exactly as at any subpanel: no bonding screw, no jumper, neutrals on an isolated bar. Older installations sometimes used a three-wire feeder with the neutral bonded at the outbuilding, and that arrangement has not been permitted for new work for some time. Run a separate equipment grounding conductor with the feeder.
Getting the power there
The trench is where most of the work is. The wiring method choice is between direct-burial cable and conductors in a raceway, and the required burial depth depends on which method you choose and what is above the trench, since a driveway and a lawn are treated differently. Those depth figures come from the code table. Whatever method you use, the conductors must be suitable for a wet location, since underground raceways fill with water. Provide protection where the wiring emerges from the ground, and think about future access: a sleeve with a pull string costs little now and saves a second trench later.
Circuits inside the building
Once power reaches the outbuilding, normal branch-circuit rules apply inside it. Garages and similar spaces have their own receptacle and GFCI requirements, and those have broadened in recent code editions to cover more of the outlets in such spaces. Lighting should be controlled at the entrance so nobody walks into a dark workshop. If the building will house a compressor, a welder or a heater, size the feeder for that rather than for lights and a socket, because upgrading a buried feeder later means reopening the trench. Sizing the feeder generously at installation is the single best decision available.
What to check before you act
- Provide a disconnecting means located at the outbuilding itself.
- Install a grounding electrode system at the structure and keep neutrals isolated there.
- Choose a wiring method and burial depth suited to what covers the trench.
- Size the feeder for the eventual load, not the first light fixture.
Common questions
Do I need a subpanel for a single circuit to a shed?
A single branch circuit may not require a panel, but a disconnecting means at the structure is still required. A small panel is often the simplest way to provide it.
Can I reuse an old three-wire feeder to a detached garage?
Existing installations may be permitted to remain, but new or replaced feeders require a separate equipment grounding conductor with neutrals isolated at the remote panel.
The practical takeaway
Powering an outbuilding is a small feeder installation with a disconnect, its own electrode system, isolated neutrals and a buried wiring method chosen for the conditions. Plan the capacity for the workshop you will eventually want, because the trench is the expensive part.
References and further reading
- NFPA: National Electrical Code overview covering feeders and separate structures
- OSHA: wiring design and protection including grounding and disconnecting means
- CPSC: home electrical safety guidance including outdoor wiring and cord misuse
Numerical scenarios are illustrative unless identified otherwise. Follow the exact product instructions; component ratings and local installation requirements can differ.
