Install an Outdoor GFCI Outlet

Power outside changes how you use your yard. A GFCI outlet on the deck or patio means no more extension cords snaking through doorways, no more choosing between leaving windows cracked or running the grill fan. You plug in string lights, power tools, a fountain pump, an electric mower, and the outlet cuts power in milliseconds if water gets where it shouldn't. The installation itself is straightforward electrical work with one critical addition: weatherproofing. Every connection must shed water, every box must seal tight, and the GFCI must trip reliably even in freezing rain. Done right, an outdoor outlet becomes invisible infrastructure. Done poorly, it becomes a maintenance problem that trips breakers or worse, a shock hazard. This guide walks through the install that lasts, from tapping an interior circuit to mounting a box that stays dry through ten winters.

  1. Turn Off Power and Locate Source Circuit. Switch off the breaker for the circuit you'll tap into, then verify power is off with a non-contact voltage tester. Choose an interior outlet on an exterior wall, ideally one that already has GFCI protection upstream or that you'll replace with a GFCI. The outdoor outlet must be on a 15 or 20-amp circuit with ground. Mark the stud locations and confirm the outlet box position from outside.
  2. Drill Through Wall and Install Outdoor Box. From outside, drill a three-quarter-inch hole through the siding and sheathing at a slight downward angle to shed water. Mount a weatherproof electrical box with a foam gasket directly over the hole, securing it to the siding or directly into a stud if possible. The box should sit flush against the siding with the gasket compressed to seal. Use corrosion-resistant screws and apply a bead of silicone caulk around the top and sides, leaving the bottom open for drainage.
  3. Run Conduit and Pull Wire. Attach a short section of weatherproof conduit from the outdoor box to the hole in the wall using a watertight connector. Inside, remove the source outlet and knock out the appropriate hole in its box for the incoming conduit or cable. Run 12-gauge or 14-gauge wire through the conduit to match your circuit size — you'll need three conductors plus ground. Leave six inches of wire extending into both boxes for connections. Secure conduit with straps within twelve inches of each box.
  4. Wire the Indoor GFCI Receptacle. At the source box, connect the incoming power wires to the LINE terminals on a GFCI outlet — hot to brass, neutral to silver, ground to green. Connect the wires running to your outdoor outlet to the LOAD terminals. This protects the outdoor outlet with upstream GFCI protection. Fold wires carefully into the box, mount the GFCI, and attach the cover plate. If the circuit already has GFCI protection at the breaker, you can use a standard outlet here instead.
  5. Wire the Outdoor GFCI Outlet. Strip three-quarters inch from each wire in the outdoor box. Connect hot to the brass terminal, neutral to silver, and ground to the green screw on the GFCI receptacle. Use wire nuts rated for outdoor use and wrap connections with electrical tape. Ensure the GFCI is rated for outdoor use and has a weatherproof rating of at least WR. The outlet should be oriented with ground hole down. Push wires into the box without pinching.
  6. Install Weatherproof Cover. Attach an in-use weatherproof cover that protects the outlet even with a plug inserted. These deep covers have spring-loaded doors and gaskets that seal around cords. Ensure the foam gasket sits tight against the GFCI face and that the cover's hinge is at the top to shed rain. Screw the cover to the box using the provided hardware. Apply a thin bead of clear silicone along the top edge where cover meets siding.
  7. Restore Power and Test GFCI Function. Turn the breaker back on and press the reset button on the outdoor GFCI. Plug in a lamp or voltage tester to confirm power. Press the test button — power should cut immediately. Press reset to restore power. Test both the indoor and outdoor GFCIs if you installed both. The outdoor outlet should also trip when you test the indoor unit if wired to LOAD terminals. Confirm ground with a three-prong tester.
  8. Seal Penetrations and Final Inspection. Check all caulk lines and conduit connections for gaps. Verify the outdoor box is secure and the cover gasket seals completely around its perimeter. Inside, confirm the source outlet box cover is tight and labeled if it provides GFCI protection for other outlets. Document the circuit you used and label the breaker in your panel. Leave the weatherproof cover closed when not in use to keep moisture out.