Understanding Your Home’s Electrical Wiring
Most homes in the U.S. are wired with a combination of 15-amp and 20-amp, 120-volt circuits.
Because 15-amp receptacles can be used with 20-amp circuits, most of the outlets you see in American homes are the standard 15-amp variety, with two slots and a U-shaped grounding hole.
20-amp receptacles have a horizontal slot branching off one of the vertical slots. Appliances, such as microwaves, often have 20-amp plugs and must be plugged into a 20-amp outlet. Electrical plugs designated as 20-amp will not fit into 15-amp outlets.
- A 15-amp circuit is usually served by 14-gauge wire and is protected by a 15-amp circuit breaker or fuse.
- A 20-amp circuit, protected by a 20-amp breaker or fuse, must be served by 12-gauge or 10-gauge wire.
Tip: The easiest way to determine whether a circuit is 15 or 20 amps is to look at the corresponding breaker or fuse in the breaker panel. Dedicated circuits are electrical lines that carry an electrical current to one single outlet. These are recommended for major appliances to ensure they have an ample and consistent stream of power for safe operation.
Determine whether you need a 3-prong vs. 4-prong cord when shopping for major appliances:
- 3-prong plugs are used for homes built before the year 2000.
- 4-prong plugs are used for homes built after the year 2000.
When you add professional installation to your new appliance purchase from The Home Depot, a compatible cord is required. The delivery agent carries both types of cords to make sure your home is covered.
When you purchase a new appliance from The Home Depot without professional installation, a 4-prong cord is sent by default. If your home is equipped with a 3-prong outlet, you will need to purchase a 3-prong cord or connector adapter separately.
Types of Electrical Outlets and Receptacles
There are a various types of electrical outlets designed to match the requirements of your appliances, power tools and electronics.
Outlets and outlet covers are available in a variety of colors, wood finishes and metals such as brass and nickel. Coordinated sets of wall switches and matching switch plates are also available.
15-Amp Duplex Receptacle
- Standard electrical outlet in American homes.
- Each of the two outlets has a long (neutral) slot, a shorter (hot) slot and a half-round grounding hole.
Combination Outlet
- Combination outlets provide two features in one device (ex: outlet with a light or a switch).
GFCI Outlets (Ground Fault Circuit Interrupter)
- A GFCI outlet protects against dangerous ground faults, which occur when electrical current travels through any abnormal path to the ground.
- Monitors the current flowing through the hot and neutral conductors to determine if any current is leaking from the circuit.
- GFCI will trip and quickly turn off power if the leakage reaches a potentially hazardous level.
- Code requires GFCI receptacles be installed in bathrooms, wet areas of kitchens, basements and outdoors.
AFCI Outlets (Arc Fault Receptacle)
- An AFCI outlet protects against electrical fires resulting from arc faults by interrupting power, reducing the likelihood of a home’s electrical system being an ignition source of a fire.
- Designed to detect a wide range of hazardous arc faults resulting from damage in branch circuit wiring and extensions to branches such as appliances and cord sets.
- Required by the National Electrical Code in many areas of the home.
Tamper-Resistant Receptacle
- Can be used in place of conventional 15-amp and 20-amp outlets.
- Required by 2008 National Electrical Code for use in new construction or renovation.
- Protects children from electrical injury with a built-in shutter mechanism that blocks insertion of most small objects; shutters only open when a properly rated electrical plug is inserted.
- Permanent once installed, offering continuous protection, unlike plastic outlet caps that can be removed.
Weather-Resistant Receptacle
- Required by the 2008 National Electrical Code in damp or wet locations, such as patios, decks and pool areas, or any other residential outdoor location.
- Available in 15 and 20-amp sizes.
- Built with UV-stabilized thermoplastic; corrosion-resistant.
- Choose from combined weather/tamper-resistant outlets or weather-resistant GFCIs with or without tamper-resistance.
- Remember: Outlets in damp or wet locations should always be installed with weather-resistant covers.
Rotating Outlet
- Can be positioned to accommodate more than one large plug from cell phone chargers, hairdryers, cordless appliances, night lights and more.
- Reduces the need for power strips.
Specialty Outlets
- Many appliances, tools and electronics require specific types of electrical outlets to operate safely and at peak efficiency.
Surge Suppression Outlets
- Designed to protect sensitive electronic equipment from power spikes without the need for power strips.
Split Circuit Receptacles
- Two outlets with each wired on a different circuit, or one outlet live and the other switched (connected to a wall switch in your home).
30-Amp or 50-Amp 125V/250V Receptacles
- Required by some heavy-duty appliances such as dryers, cooking ranges or power tools.
- Has a special prong configuration.
Ungrounded or Ungrounded/Unpolarized Outlets
- Usually found in homes built before the mid-1960s.
- Similar to standard duplex receptacles in that they accommodate two-prong electrical plugs, but are missing the U-shaped grounding hole.
- Polarized with one long (neutral) slot and a shorter (hot) slot.
Tip: If your home was built with these outlets, you may want to upgrade the wiring before replacing an ungrounded or ungrounded/unpolarized outlet with a grounded one.
USB Outlets
- Wall socket with one or more USB ports built in.
- Allows recharging of devices direct from USB cable.
- Leaves regular outlets free for use by other appliances.
Smart Outlets
- Replaces a traditional outlet; does not require an adapter.
- Allows control of outlet from smartphone.
- Uses z-wave communication; requires a smart home hub for use.