How to Install an Outdoor Receptacle
You can install an outdoor electrical receptacle safely and quickly by using a through-the-wall technique. It is important to understand wiring basics, use proper safety precautions and have your work inspected by your local building code official. This method works with homes that do not have stone or brick exteriors where the outlet is installed.
Tools and Materials
Cordless Drill/driver with a ¼-inch 18-inch long drill bit (available in the electrical tool section of your local hardware store or home center)
Electrical fish or wire coat hanger
Exterior electrical box
Weatherproof box cover
In just a few hours you can install a new receptacle by running a new wire from an existing interior outlet and install the new exterior outlet on the opposite side of the wall. In many cases you can surface-mount the new outlet box on the siding instead of cutting a hole in the siding.
Call your local inspections department to apply for a permit before you begin an electrical installation.
Building codes prohibit tapping into circuits in kitchens, bathrooms, laundry rooms or into receptacles dedicated to large appliances, like a refrigerator. Select living room, bedroom and basement circuits, but don't tap into a circuit that's already overloaded and trips the circuit breaker.
1. Locate the Receptacle
Turn off the circuit breaker controlling the outlet and test that the power is off with a voltage tester. Remove the outlet cover and receptacle from the electrical box and unscrew the wires from the receptacle. Make sure the box is large enough to hold an added set of wires as an overstuffed box is a fire hazard. Most metal boxes are too small to hold additional wires. See my article discussing electrical box sizing - http://electrical-systems-lighting.knoji.com/how-to-choose-the-correct-size-electrical-box/
Depending on the size of the box, you may have to remove it and install an old-work box with sufficient size.
Old Work Box
With a stud sensor locate the stud alongside of the interior receptacle and mark the location as you will want to drill on the opposite side of the outlet to keep away from the wiring. You will also be installing the outlet in the same stud cavity to speed up the installation and reduce the amount of drilling and drywall patches. To locate the exterior receptacle drill a 1/4-in. hole alongside an existing electrical box to mark the location of the new outlet. On the exterior side of the wall, drill a 3/4-in. or 1-in. hole in the siding along the edge of the ¼-inch hole.
Warning - If you have aluminum wiring, call in a licensed electrician who is certified to work with it.
2. Running the new wire
The new wire must be the same gauge as the wire already in the box, which is either 12 or 14 gauge. Check the cable size marked on the sheathing or use your wire strippers as a gauge.
If the outlet box is large enough to support the additional wires remove a knockout in the box by hitting it with a screwdriver.
Strip the sheathing off the end of the new cable and tape the remaining wire to the sheathing to form a narrow loop. Feed the loop through a knockout in the interior box about a foot or so. Fish for the cable from the exterior hole using a hook made from a coat hanger or a scrap piece of wire and pull the cable through the hole. Pull out at least 12 inches of cable so you have enough wire to work with.
3. Wire the interior receptacle
At the interior box, cut the cable to leave about 10 inches remaining. Remove the sheathing to expose the wires. To make pigtails, cut 6-in. pieces of black, white, and bare copper wires from the coil of cable and strip 3/4 in. of insulation off both ends. Screw one end of each pigtail to the receptacle: The bare copper goes to the green ground screw, the white to one of the silver screw terminals, and the black to one of the brass screw terminals.
Using wire nuts, connect all of the black (or red) wires together, all the white wires together, and all of the ground wires (green or bare copper) together.
Gently fold the wires into the box, then reattach the outlet and cover plate.
4. Wire and Mount the exterior GFCI Receptacle
Reminder - Outside outlets must be GFCI protected.
Fasten a clamp to the hole in the back of the box, then feed the cable through the clamp. Apply a heavy bead of silicone caulk around the clamp and place the box on the wall, inserting the clamp into the hole in the siding. If you do not have a surface mount outlet box, attach two mounting lugs on opposite corners to the back of the metal electrical box.
If you have clapboard siding or plywood sheathing, mount the junction box to the house, using exterior-grade fasteners such as galvanized deck screws through the mounting lugs. For vinyl siding use plastic hollow wall anchors.
Strip the insulation of the wires and attach the ground wire to the green screw in the box and to the green screw on the GFCI outlet. Make sure to identify the line, hot and white terminals. Attach the black wire to the brass screw or adjacent push-in hole and the white wire to the silver screw or push-in hole. Carefully fold the wires into the box and screw the outlet in place. Install a weather-proof exterior outlet cover.
Restore power to the circuit and test the exterior and interior receptacles for proper operation.