What You’ll Need
This USB Outlet is a great project for electrical beginners, and everything you need is available at a home center. If you don’t own any electrical tools, expect to spend about $15 on the basics.
Before you shop, determine whether your cable is 12- or 14 gauge; you’ll need the same size cable for your new outlet. For reference, 12-gauge wire is about the thickness of a nickel, and 14-gauge is about the thickness of a dime.
The new junction box you’ll use is called an “old work” box. It mounts on drywall and doesn’t need to be fastened to a stud. We chose a “two-gang” box that allows for a second outlet. It also requires a larger hole in the wall, which makes feeding cable into the existing box much easier.
Outlets with USB outlet ports come in various configurations and cost $15 to $30 at home centers. For a wider selection, shop online. To comply with electrical code changes, you may have to buy an AFCI outlet ($30) to replace the existing outlet. Ours is protected by an AFCI circuit breaker.
USB ports don’t draw much power, so you can add a USB outlet to any existing outlet except a switched outlet or a dedicated outlet for an appliance, such as a stove or refrigerator. Once you’ve chosen your power source outlet, switch off the breaker for that circuit. Then use a noncontact voltage tester to verify that the power is off.
You May Need a Larger Junction Box: Electrical codes contain strict rules about how many wires, connectors, switches and outlets can go in a junction box. Since you’re adding wires, your existing box may not be large enough according to code. To see the formula, go to familyhandyman.com and search for “adding a receptacle.” For help installing a larger box, search for “crowded electrical box.”
Wiring the new outlet
At the new junction box, each wire from the cable needs two pigtails, as there are two outlets. Strip the wires and use wire nuts to connect two black pigtails to the black wire, two white pigtails to the white wire and two bare copper pigtails to the ground wire. Connect the pigtails to their corresponding terminals on each outlet. If your USB outlet has prewired leads, use those in place of pigtails for that outlet.
Wiring the existing outlet
You’ll have three cables in the existing box: a power supply, a line feeding downstream outlets and your new cable. Make a pigtail from each colored wire. Connect each pigtail with the rest of the same colored wires from each cable, using wire nuts. Connect the pigtails to their corresponding terminal on the old outlet.
1. Find the studs
Locate the two studs that flank the existing outlet (Photo above) and find a good position in the wall cavity for the new outlet.
2. Trace the box
Hold the new “old work” box in place against the wall, making sure it’s plumb and level, and then trace around it (Photo above).
3. Cut the hole
Cut the hole as accurately as possible (Photo 3). An “old work” box relies on a snug fit in the cutout for stability, as it’s not attached to a stud. If your new outlet is on an exterior wall, use a box that maintains the vapor seal to keep out drafts. It’s also important to test fit the box and enlarge the hole slightly if needed.
4. Run the cable
Disconnect the old outlet and then feed the new cable to the existing box. Don’t skimp on cable; a little extra inside the wall is good, and you’ll trim the ends when you’re ready to make the connections. Run cable into the new box, and then mount the box to the wall (Photo above).
Caution: If your wires are dull gray rather than the dark orange color characteristic of copper, they may be aluminum. Making safe connections with aluminum wiring requires special connectors and techniques not covered here.
5. Make the connections
Connect the wires and receptacles in both boxes (Photo above and Figures A and B). Our USB outlet came with lead wires. Yours may have terminal screws like those on standard outlets. Mount the outlets, reinstall the faceplates, turn the power back on and test the outlets.