A 20-amp receptacle has a T-shaped neutral slot and will accept a 20-amp plug; a 15-amp receptacle has two parallel slots and will not. On a US branch circuit supplying several outlets, a 15-amp receptacle is permitted on a 20-amp circuit, and the code requires 20-amp circuits in kitchens, laundries, bathrooms and garages rather than 20-amp receptacles.
In short
- The visible difference is one slot: 5-15R has two parallel slots, 5-20R adds a T.
- Where a branch circuit feeds two or more outlets, a 20-amp circuit accepts 15- or 20-amp receptacles; a 15-amp circuit accepts 15-amp receptacles.
- US code requires 20-amp branch circuits in named locations. It does not require you to buy a 20-amp receptacle face.
- All four Studio Timeless outlets sell a 15A/20A choice. The 20A costs $5 more on exactly one of them, the GFCI.
- On our duplex outlet, the two amperages carry two different certification sentences. On our dual USB-C outlet, the page tells you to buy a different product for 20A while the menu sells 20A.
The amperage option is a choice about the device, not about your wiring
Picking 20A in a drop-down does not change the wire in your wall, the breaker in your panel, or what the circuit can carry. It changes which receptacle you receive. A circuit's capacity is set by its conductor size and its overcurrent device, both decided when the house was wired. The receptacle is the last component in that chain and has to suit the circuit it lands on. This is the most common misunderstanding in our pre-sale questions: you are not upgrading a circuit when you buy a 20-amp outlet, you are choosing a device to match a circuit someone else already sized.
The physical difference is one slot
A 15-amp 125-volt receptacle carries the NEMA 5-15R configuration, with two parallel vertical slots and a round ground. A 20-amp receptacle carries 5-20R, which keeps the same ground and the same hot slot but turns the neutral slot into a T, so that a 20-amp plug with its sideways blade can enter. A 20-amp receptacle therefore accepts both 15- and 20-amp plugs, while a 15-amp receptacle accepts only 15-amp plugs. That asymmetry is the whole point of the configuration system. ANSI/NEMA WD 6 is the standard that fixes these shapes, and its own scope says it covers dimensional requirements and does not cover performance. A configuration is a promise about what will physically mate, not about how well the device is built.
A 15-amp receptacle on a 20-amp circuit is normal, not a compromise
Where a branch circuit supplies two or more receptacles or outlets, the National Electrical Code table of receptacle ratings permits 15- or 20-amp receptacles on a 20-amp circuit. The North Carolina Office of the State Fire Marshal has published a formal interpretation making the point, including the detail most people miss: a duplex receptacle is two receptacles, not a single receptacle, so a duplex on a 20-amp circuit is governed by the multiple-outlet rule. This is why almost every 20-amp kitchen circuit in America is populated with 15-amp duplex receptacles and passes inspection.
The reverse is restricted, and the rule is narrower than it is usually quoted
People repeat that a 20-amp receptacle may never go on a 15-amp circuit, which is close enough for most buyers but not exact. The restriction lives in the receptacle-rating table, and that table applies to circuits supplying two or more receptacles or outlets, where a 15-amp circuit limits you to receptacles not over 15 amps. A single receptacle alone on an individual branch circuit is handled by a different sentence requiring the receptacle rating to be not less than the circuit rating. We flag the gap rather than teach anyone to exploit it: on an ordinary multi-outlet residential circuit the practical rule holds, and a dedicated single-appliance circuit is a conversation for your electrician and your inspector.
Code requires 20-amp circuits, not 20-amp receptacles
This distinction decides most orders. The rooms people associate with 20 amps are rooms where the code requires 20-amp branch circuits: two small-appliance circuits serving kitchen countertops, at least one laundry circuit, at least one bathroom circuit, and at least one garage circuit. Minnesota's Department of Labor and Industry publishes an inspection checklist for one-family dwellings that states them as an inspector reads them: two 20-amp circuits for kitchen receptacles, one for laundry, one for bathroom, one for garage. The International Association of Electrical Inspectors walks the same sections. Nothing in that list obliges you to install a receptacle with a T-slot. The obligation attaches to the circuit; the receptacle choice is then opened back up by the rating table.
A 15-amp face can be rated 20 amps inside
A receptacle on a multi-outlet circuit has to pass current through to everything downstream of it, which is why the face configuration and the internal rating are two different numbers. NEMA's own wiring device FAQ states that 15-amp receptacles are tested and listed to carry 20 amps from terminal to terminal, with the 15-amp number describing what the plug contacts accept. UL made the same point for ground-fault devices in an answer published on its own code-authorities site, noting that the contact rating has to be marked on the device. The marking is the evidence of what a device is rated at, not the shape of the slot.
What our four outlets actually sell
We read all four of our active outlets in full on 11 November 2026, variant by variant rather than from the option menus, and the four treat the same two-value option four different ways. The table is the article.
| Outlet | How the amperage is labelled | 15A price | 20A price | What the page says about amperage |
|---|---|---|---|---|
| Solid Brass Duplex Outlet | 15 / 20 | $60 | $60 | Two separate certification sentences, one per amperage |
| Solid Brass GFCI Outlet | 15A / 20A | $60 | $65 | One sentence covering both; amperage also appears in the title |
| USB-A + USB-C Charging Outlet | 15A / 20A | $60 | $60 | Nothing at all |
| Dual USB-C Outlet | 15A / 20A | $70 | $70 | States it is a 15A device and points you to another product for 20A |
Unlacquered Antique Brass adds $14 to each of those figures, on every one of the four. It is hand finished and made to order, with about three weeks of production before shipping, and it is not returnable, so it is the one finish worth confirming with a sample before you commit a whole house.
The surcharge exists on one product out of four
Only the GFCI outlet charges more for 20 amps: $60 against $65 in the lacquered finishes, $74 against $79 unlacquered, consistently across all ten finishes. The duplex, the USB-A + USB-C outlet and the dual USB-C outlet charge the same for either amperage. We are not going to invent a story about why. What we can say is that the difference is real, small, and not a rule that runs across the catalogue. If you are costing a whole floor, the only amperage line that moves your total is the GFCI count.
On the duplex, the amperage changes the certification sentence
Our own duplex page uses two different sentences for the two amperages, and they do not have the same scope: the 15-amp device is described as listed for use in the United States and Canada, and the 20-amp device is described as UL listed. We are not reproducing the marks or the file reference here, because the Canadian scope of our devices is a question we currently have open internally and we would rather publish the gap than a confident answer. The practical advice is short. For a US project, either amperage is documented. For a Canadian project, or any jurisdiction asking for a bi-national listing, ask us in writing before you order and we will answer with what the manufacturer has confirmed to us rather than with what the web page says. We never confirm a certification scope without that written confirmation, and this is a live example of why.
One of our pages sells an option it tells you not to buy
The dual USB-C outlet publishes a rating paragraph stating that it is a 15A device, that its two ports share about 24 W in total at 5 V and 4.8 A, and that anyone who needs a 20-amp receptacle should choose the USB-A + USB-C outlet instead. Directly above that paragraph, the AMP menu sells a 20A, and those variants are purchasable in every finish. The description and the buy box disagree, and the buy box wins, because a customer can complete that order today. We publish it because it is ours, and because a reader choosing between those two outlets deserves to know the page is not internally consistent. Until it is resolved, treat the written rating as the one to trust and use the USB-A + USB-C outlet where a 20-amp charging receptacle is genuinely wanted.
Ground-fault protection is decided by location, and not by amperage
The amperage option and the ground-fault question are independent, and conflating them causes real ordering mistakes. US code sets out ground-fault protection as an enumerated list of locations: bathrooms, garages and accessory buildings, outdoors, crawl spaces, basements, kitchens, areas with sinks and food preparation, boathouses, indoor damp and wet locations, plus three entries measured in feet rather than named by room, covering receptacles within six feet of a sink bowl, within six feet of a tub or shower, and within ten feet of a laundry hookup. It is not a judgement call about being near water, and it is not triggered by picking 20 amps. Our guide to installing a GFCI outlet covers the locations, and our comparison of duplex, GFCI and USB-C outlets covers which of ours fits where.
What the amperage option does not change
It does not change the plate. All four outlets ship as complete monobloc assemblies, plate and receptacle together, which is the opposite of the American convention of buying a device and a cover plate separately, and it is the thing we explain most often. It does not change the opening: all four use the rectangular Decorator-style opening, so both amperages land in the same outlet plate geometry. It does not change the ten finishes. It does not change the box, covered in our piece on box types and sizes. And it does not change the screws: every gang takes two, so a 1-gang takes two and a 5-gang takes ten.
How to decide, in four questions
Ask what the breaker is, first: a 15-amp breaker on 14-gauge wire means a 15-amp receptacle. Ask next whether anything on the circuit carries a 20-amp plug, usually a window air conditioner or a large shop tool; if nothing does, the T-slot buys you nothing. Ask third whether the location requires ground-fault protection, because that decides the product, not the amperage. Ask fourth whether a specifier or an inspector has written an amperage into a document you must satisfy, in which case match the document. If the answers conflict, our installation and compatibility page is the next stop, and sending us your plan is faster than guessing.
What we publish about our outlets, and what we do not
We apply to our own pages the test we recommend for anyone else's. No US rule obliges a manufacturer to publish any particular line on a commercial specification sheet, which is why three competing 20-amp receptacles from three large manufacturers publish three different sets of figures. Here is where we stand.
| Line | Do we publish it? |
|---|---|
| Amperage option, 15 and 20 | Yes, on all four outlets |
| Price by amperage | Yes, visible in the variant |
| Certification wording | On two of four; inconsistent between them |
| USB power output | On the dual USB-C only, at about 24 W total |
| Plate thickness, 0.080 in | Yes |
| Screw size, 1.97 in with a 0.28 in slotted head | Yes |
| Terminal torque value | No |
| Overload or endurance cycles | No |
| Country of manufacture | No |
| Multi-gang derating table | No |
Four of those gaps are ours to close and we have said so before. Our article on how to read an electrical spec sheet explains why an absent line is not an answer, and our piece on verifying a certification mark explains how to check a claim rather than take it.
Before you touch a wall box
Switch off the breaker for the circuit, then verify the conductors are dead with a tester you have just proved on a circuit you know to be live. Work de-energised. Live testing belongs to qualified persons with the training and equipment for it. Replacing a receptacle on an existing circuit is permitted homeowner work in many jurisdictions and not in others, and adding a circuit, moving a box or altering wiring commonly requires a permit and a licensed electrician. Your local code and your authority having jurisdiction decide, and both can be stricter than the national code. Our articles on permits and licensed electricians, on what an inspector can and cannot require and on replacing an outlet safely set out what that means in practice.
Frequently asked questions
What is a 20 amp outlet?
A receptacle built to the NEMA 5-20R configuration, with a T-shaped neutral slot that accepts both 15- and 20-amp plugs, intended for a 20-amp branch circuit.
Can I put a 20 amp outlet on a 15 amp circuit?
On an ordinary circuit feeding two or more outlets, no: the receptacle-rating table limits a 15-amp circuit to receptacles not over 15 amps. A single receptacle on an individual branch circuit is treated separately, and that is a question for your electrician.
Is a 15 amp outlet safe on a 20 amp circuit?
Yes, and it is the usual arrangement. The code table permits 15- or 20-amp receptacles on a 20-amp multi-outlet circuit, and NEMA states that 15-amp receptacles are tested and listed to carry 20 amps terminal to terminal.
Does the kitchen need 20 amp outlets?
The code requires at least two 20-amp small-appliance branch circuits serving the countertop. It does not require the receptacles on them to be 20-amp devices.
What is a 20 amp GFCI outlet?
A ground-fault device on the 5-20R configuration. Ours is the only one of our four outlets that costs more at 20 amps, $65 against $60 in the lacquered finishes.
How do I tell a 15 amp outlet from a 20 amp outlet?
Look at the neutral slot. Two parallel slots is 15 amps; a sideways T is 20 amps. For the rating rather than the configuration, read the marking on the device itself.
Do your outlets come with the wall plate?
Yes. All four are complete monobloc assemblies, plate and receptacle together. Plates sold on their own in our wall plate collection are for third-party devices and do not fit our integrated units.
Is there a 20 amp option on the dual USB-C outlet?
The menu currently offers one and the written rating on the same page says the product is a 15A device and points to the USB-A + USB-C outlet for 20 amps. Trust the written rating, and ask us before ordering.
Does 20 amps charge a phone faster?
No. The receptacle amperage describes the branch circuit it suits. USB output is a separate figure, and on our dual USB-C outlet the two ports share about 24 W in total.
Choosing an amperage is the smallest decision on an outlet order and the one most often made for the wrong reason. Start from the breaker, let the room decide the ground-fault question, and spend the attention you saved on the finish. Our brass outlet collection carries all ten, and a finish sample set settles that better than any screen.
Last updated: November 11, 2026
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