When I started my electrical apprenticeship, I didn’t know much about amps, outlets and electrical circuits. I had swapped out a few light fixtures and even installed a new dishwasher. But when it came to the technical jargon, I was a little lost.
As a new homeowner, you may likewise be confused by the available choices when doing electrical repairs and upgrades. One thing that trips people up is the difference between 15-amp and 20-amp outlets, aka receptacles. They sell both kinds at home centers and hardware stores, so how do you know which one goes where?
This guide can help. First, we’ll clear up some terminology. Then we’ll walk you through the differences and where to use them. Remember, there’s no shame in asking for help from a licensed electrician (like me!). Your safety is always paramount.
Outlet vs. Receptacle
Before we get into the differences between 15-amp and 20-amp “outlets,” we need to agree on some terms.
If you’re reading this, you’re likely talking about the thing on the wall where you plug in your computer and TV. While colloquially called an outlet, the device on the wall (or power bar) that receives the plug is actually called a receptacle.
Receptacles are installed at an outlet, but don’t let this confuse you. This distinction should help you understand the difference:
Outlet: A point on the circuit where electricity is taken to supply equipment. Think of an outlet as a location, not a device.
Receptacle: A device installed at an outlet for the connection of a plug.
Receptacle outlet: An outlet where one or more receptacles is installed.
What Is an Amp?
Amperes, aka amps, are units of electrical current, which is the organized flow of electrons through an electrical circuit. It’s these electrons that make our stuff run, from appliances to motors to lights. Amps describe the rate at which the electrons move through the circuit.
One common way to visualize an amp is water flowing through a garden hose. The more you turn on the faucet, the stronger the flow of water. If we wanted to, we could measure the amount of water that moves past a point on the hose in one second.
Swap out water in a hose for electricity in a circuit, and you’re describing an amp. The number of amps a tool, appliance, light and any other electrical device needs to operate dictates many electrical decisions, from the size of your circuit breakers to how big of an extension cord to buy.
Receptacle Rating vs. Branch Circuit Rating
Another concept that’s important to know before choosing a receptacle is the difference between the circuit rating and the receptacle rating.
When buying a receptacle, you can’t just match the circuit rating and the receptacle rating and call it a day. The National Electric Code (NEC) sets out specific requirements.
Here are some more terms to know:
Branch circuit: These are the circuits that “branch” out from the main panel and power your home.
Branch circuit rating: Describes the amount of current that can safely be carried on the circuit. This is determined by the overcurrent protection (aka circuit breaker) protecting the circuit.
Receptacle rating: Describes the amperage the receptacle itself can handle.
Though our homes have 15-amp and 20-amp branch circuits (and larger ones for specific appliances), the rating of a receptacle and the rating of a circuit it’s installed on do not necessarily correspond. We’ll dig into the details below.
Differences Between a 15-Amp Receptacle and a 20-Amp Receptacle
The first thing you’ll notice about a 15-amp receptacle and a 20-amp one is the physical difference.
A 15-amp receptacle looks like the ones you see in your home, at the office and in public places every day: two vertical slots and one roundish one. (They kind of look like faces.) A 20-amp receptacle, in contrast, more resembles a face that’s winking. One of the vertical slots also has a horizontal aspect, like a sideways “T.”
Why have different shapes? As with many deliberate design choices in the electrical industry, it’s a safety thing.
Plugs that correspond with 20-amp receptacles have one vertical and one horizontal blade, and thus cannot fit into a 15-amp receptacle, which lacks the “T” -shaped slot. This prevents people from plugging in an appliance that’s more powerful than the 15-amp receptacle and circuit can handle.
Here’s When You Need a 15-Amp Receptacle
Think about the things you use every day: computers, televisions, vacuum cleaners, toasters, coffee makers, refrigerators, shop tools and microwaves. What do the plugs look like?
Unless they’re of the two-prong variety, they’re generally three-prong plugs with two vertical blades and one round one. Most standard, everyday appliances found in homes draw less than 15 amps, usually much less.
These common items are compatible with 15-amp or 20-amp circuits. But what about the receptacle? That depends.
If you have a circuit rated 15 amps, the NEC requires that you use 15-amp receptacles. Full stop. Fifteen-amp circuits use electrical conductors (aka wires) that aren’t big enough for appliances that draw more than 15 amps. If you put 20 amps on a 15-amp circuit, you’ll trip the breaker. It’s also unsafe.
If your circuit is 20 amps, you can install a 15-amp receptacle, but only if you have multiple receptacles on the same circuit, like the common two-plug (“duplex”) or four-plug (“quad”) setups you have all over your house. (This is why you probably have 15-amp receptacles in your kitchen and bathroom, even though the circuits are 20 amps.)
If this sounds strange, there’s a good reason. Even with multiple receptacles on a single circuit, it’s unlikely you’ll be plugging in and running everything at once.
However, if you have a single receptacle on a dedicated, 20-amp circuit — meaning the circuit’s only designed for one plug and one piece of equipment — you must use a 20-amp receptacle. Single receptacles dedicated to one appliance tend to be used for things where it would be problematic if it failed, like a sump pump, or large refrigerator or freezer.
Here’s When You Need a 20-Amp Receptacle
Look around your house — how many winking-face receptacles do you see? Probably not many.
Think about all the plugs in your house, too. Can you remember any of them having one vertical blade and one horizontal? That number is likely even lower.
That’s because appliances that draw close to 20 amps are rare in regular residential use. The sump pump and large refrigerators and freezers mentioned above, window air conditioners, larger shop tools and commercial kitchen appliances are a few things that might need a 20-amp receptacle.
Sometimes, builders or electricians put in 20-amp receptacles because they’re sturdy and can accept either a 15-amp or a 20-amp plug. This is OK, if needlessly expensive, as long as they’re on a 20-amp circuit.
Never put a 20-amp receptacle on a 15-amp circuit. That’s a code violation.