How to Add an Outdoor Outlet From an Indoor One (2024 Guide)

TL;DR: You can add an outdoor outlet from an existing indoor outlet if that indoor circuit has spare capacity and, ideally, GFCI protection already built in. Expect to drill one hole through the wall, run NM-B cable to an in-use weatherproof box, and spend $80-$200 on parts if you do it yourself. Any exterior outlet must be GFCI-protected and covered by an in-use (bubble-style) cover, per the 2020 National Electrical Code.

_Last reviewed: July 2026 · 7 min read_

You've got an indoor outlet on the wall that backs up to your patio, and running power to the outside seems like it should be simple. It mostly is, but a few wrong turns (wrong wire gauge, no GFCI, a cheap cover) turn a $100 project into a rewiring job or a wet outlet that trips every time it rains.

Okoniq Property Hub helps you log which outlets are GFCI-protected, when the exterior cover was last inspected, and what circuit each one sits on, so you're not guessing six years from now.

Can you tap an indoor outlet to power an outdoor one?

Yes, as long as the indoor circuit has room for the added load and is protected by a GFCI breaker or GFCI outlet upstream. Most 15-amp or 20-amp circuits in a home run well under capacity, so adding a single outdoor receptacle for lights, a pressure washer, or holiday decorations rarely overloads anything.

The catch is GFCI protection. The 2020 NEC requires every outdoor receptacle to have ground-fault protection. If your indoor outlet already has a GFCI outlet or is on a GFCI breaker, you can wire the exterior outlet downstream of it and you're covered. If it doesn't, you'll need to install a GFCI outlet either at the indoor location or install the outdoor outlet itself as a GFCI unit. This is also a good moment to confirm your home doesn't have aluminum wiring feeding that circuit, since aluminum branch circuits need different connectors and shouldn't be spliced casually.

What parts and tools do you actually need?

You'll need NM-B cable (12-2 for a 20-amp circuit, 14-2 for 15-amp), a weatherproof exterior box, an in-use bubble cover, a GFCI outlet rated for outdoor use, wire connectors, and a drill with a long spade or hole saw bit. Total parts typically run $80 to $200 depending on cable length and box quality.

For tools, a fish tape or stiff wire helps pull cable through the wall cavity if the run isn't a straight shot. A voltage tester (non-contact and a plug-in tester) is non-negotiable, both before you open the indoor box and after you finish, to confirm the new outlet is wired correctly and dead when you're working on it.

| Item | Budget option | Better option | |---|---|---| | Outdoor box | Standard weatherproof box, ~$8 | Recessed weatherproof box, ~$18 | | Cover | Flip-lid cover, ~$6 | In-use bubble cover (works with cord plugged in), ~$15 | | Outlet | Basic GFCI, ~$15 | Weather-resistant (WR) GFCI, ~$22 | | Cable | 14-2 NM-B, ~$0.50/ft | 12-2 NM-B for future load headroom, ~$0.75/ft |

How do you actually run the wire through the wall?

Find the shortest straight path, drill a single hole angled slightly downward toward the outside, and pull the cable through with a fish tape. Start by shutting off the breaker for the indoor circuit and confirming it's dead with a tester at the outlet before you touch anything. Remove the indoor outlet, note which wires are hot, neutral, and ground, and drill your exterior hole roughly level with or slightly below the indoor box so water can't run down into the wall cavity.

Feed the new NM-B cable through the hole from outside, connect it into the indoor box using proper connectors (not just twisted and taped), and mount the exterior box with its cable clamp secured. The exterior box should sit flush against the siding with a bead of exterior-grade caulk around the penetration, never left as a bare gap. If you're also swapping a nearby ceiling light fixture or doing other electrical work in the same session, it's worth having the panel schedule labeled so you're not hunting for breakers twice.

What makes an outdoor outlet code-compliant and weatherproof?

Two things matter most: GFCI protection and an in-use cover, meaning a cover that keeps the outlet protected from rain even with a cord plugged in. A standard flip-lid cover only protects the outlet when nothing is plugged in, which fails the "wet location" requirement anywhere exposed to rain or sprinklers.

Buy a weather-resistant (WR) rated GFCI outlet, not a standard indoor GFCI, since WR units have coatings that resist moisture and UV breakdown. Mount the box with the cable entry at the bottom or side, never the top, so water sheds away from the connection point. Test the GFCI monthly using the test/reset buttons, the same habit worth building for bathroom fixtures and any childproofing electrical work you've done elsewhere in the house.

Do you need a permit or inspection for this?

Many jurisdictions require a permit for new circuits or outlets, even simple additions, though rules vary widely by city and county. Some allow homeowners to pull their own permit for work on a home they occupy, while landlords in a rental property often need a licensed electrician regardless of the scope. A $50-$150 permit fee is cheap insurance against a failed home sale inspection or an insurance claim denial down the line if the wiring wasn't up to code.

If you're closing up a rental or vacation property for the season, check that the new outdoor outlet is covered and de-energized appropriately as part of your routine, similar to the steps in closing up a seasonal home for months away.

FAQ

How much does it cost to hire an electrician for one outdoor outlet?

Most electricians charge $150 to $350 for a single outdoor outlet added from an existing indoor circuit, including the permit if required, with higher costs if the wall requires opening drywall or the run is longer than 10 feet.

Can I use an extension cord instead of adding a real outlet?

Running an extension cord outdoors long-term violates most electrical codes and voids many homeowner's insurance claims tied to fire damage, so it's not a substitute for a permanent GFCI-protected outlet even for occasional use like holiday lights.

What gauge wire do I need for an outdoor outlet?

Use 14-gauge (14-2 NM-B) for a 15-amp circuit or 12-gauge (12-2 NM-B) for a 20-amp circuit; matching the wire gauge to the breaker amperage is required by code and prevents overheating.

Why does my new outdoor outlet keep tripping?

A GFCI trips when it detects even a tiny current imbalance, often from moisture inside the box, a damaged cord, or a loose wire connection, so check the cover seal and connections before assuming the outlet itself is defective.

Is it safe to put an outdoor outlet near a hose bib or sprinkler head?

Keep at least 3 feet of separation where possible and always use an in-use weatherproof cover, since direct water spray on an uncovered outlet, even a GFCI one, can still cause corrosion and premature failure over a few seasons.

This is educational information, not electrical or legal advice. Call a licensed electrician if you're unsure about wire sizing, panel capacity, or local permit requirements before opening any electrical box.