How to find a power source

This technique only works if you can use an outlet as a power source that’s opposite, or nearly opposite, the place where you want your new outlet. To determine how to wire an outlet and whether you can safely use existing electrical outlets, follow the list below.

You can use an outlet when:

  1. If a switch or outlet is on a circuit that often blows its breaker or fuse, don’t make matters worse by adding yet another outlet to the circuit.
  2. Electrical codes restrict the number of lights or electrical outlets that can be connected to one circuit. Typically, you can have no more than eight lights or electrical outlets on a 15-amp circuit. To determine the amp rating of a circuit, just look at the number on its breaker or fuse in your main electrical panel. Turn off the circuit and test light switches and other outlets to determine exactly which lights or outlets are on a given circuit.
  3. Most electrical codes now require outlets in kitchens and bathrooms to be on separate 20-amp GFCI circuits. So before using the method we show here for how to wire an outlet in a kitchen or bathroom, check with an electrical inspector. If you add an outlet to a kitchen or bath, it must be GFCI protected. Don’t power your new outlet from a kitchen or bathroom outlet.
  4. Codes also limit the number of wires that can enter an electrical box or electrical receptacle , depending on the inside volume of the box and the gauge of the wires. The outlet-addition methods we show here are based on the most common wiring (14-gauge wire on a 15-amp circuit) and an 18-cu.-in. box (typical inside dimensions are about 2 in. x 3-1/4 in. x 3 in. deep). If the circuit is 20-amp—which means thicker, 12-gauge wire—or if the existing box is smaller than 18 cu. in., you can’t wire a new outlet as we show here unless you replace the existing box with a larger one. Plastic box sizes are stamped on the inside at the back.

Always confirm the required box size with your local building inspector. In most regions, you have to obtain an electrical permit for this work from your local building department. This helps ensure a safe job.

If you are ever in doubt, please seek professional help from companies such as Electric by Sullivan.