What size electrical wire should you use when hooking up an electrical receptacle (wall plug or electrical outlet)?

Here we explain the choice of No. 14 or No. 12 copper wire for 15A and 20A electrical circuits where receptacles are being wired.

This article series describes how to choose, locate, and wire an electrical receptacle in a home. Electrical receptacles (also called electrical outlets or "plugs" or "sockets") are simple devices that are easy to install, but there are details to get right if you want to be safe.

Electrical Wire Size & Run Length FAQs

These questions and answers about how to determine the correct electrical wire size when wiring an electrical receptacle (also referred to as "wall outlet, wall plug, etc) were posted originally

at SIZE of WIRE REQUIRED for ELECTRICAL RECEPTACLES - please check the wire size guidelines given there.

On 2018-12-17 by (mod) - use #14 copper for a 15-A receptacle circuit, but watch out for amateur wiring mistakes

Cleta

Normally a 15 amp electrical receptacle circuit is wired with number 14 copper wire.

Watch out, even if you're permitted to do electrical work yourself where you live most likely that work needs to be done with a permit and with inspections by your local electrical inspector. Don't treat that as an inconvenience it's an important safety inspection that could save your life or your house. .

Watch out also, as if you're not familiar with proper and safe electrical wiring you could burn down the building, be shocked, or be killed.

On 2018-12-16 by Cleta - what wire gauge to I use for plugins

I am trying to redo electrical to plugins I am not sure what gauge wire

On 2018-04-27 by (mod) - ok to use a much larger electrical wire?

Terrill

One might think so, but in fact unless you have room in the Box two pigtails some smaller diameter wire you'll find that the number 8 does not fit the connectors on the electrical receptacle

On 2018-04-27 by Terrill

Can I use oversized wire awg #8 thhn 120 V 20 amp outlet?

On 2018-04-25 by (mod) - use an electrical box extender

I would not rely on a home-made nor any other non-standard wire connection nor would I bury a piggy-backed wall plug in a wall - that'd be asking for future hell for anyone troubleshooting the circuit and might also be unsafe.

I would install a larger or deeper electrical box if necessary to contain the connectors to simply extend the too-short wires.

UL Listed or CSA listed electrical box extensions are sold for the purpose and can be simply retrofitted to the front of the existing electrical box.

Shown here is Raco's 1 7/8" deep single gang drawn "handy box" for extnding an electrical receptacle box about the right amount for the added thickness of your new wall.

Electrical box extenders are sold in a wide range of thicknesses or depths as well as in various box sizes that can meet most situations.

On 2018-04-25 by Bob - can I stack up electrical outlets in a creative way to bring the receptacle forward when adding wall insulation?

I'm adding 2 inches of foam insulation to my wall . I need to extend my outlets out by 2 inches , but one outlet doesn't have any extra wire in the box to extend to new outlet.

Any way to plug into front of old outlet then wire to new outlet ?

On 2018-04-13 20:14:15.398262 by (mod) -

Chris you would use 14/2 WG copper wire (WG = with ground) to wire residential "outlets" or wall receptacles on a 15Amp circuit. Do not add new circuits that don't include the grounding conductor.

On 2018-04-13 17:06:36.406303 by Chris

Can i leagally per nec use 14 2 for home residental outlets

On 2018-02-18 02:07:27.162728 by (mod) -

#12 wire is typically for a 20A circuit, not 30A

On 2018-02-17 11:02:09.492050 by COBE

FOR A 30 amps appliacbe for #12 thhn/thwn wire and how many outlets

On 2018-02-12 23:06:34.758374 by (mod) -

For a 20-Amp circuit use #12 copper wire (or #10 copper-clad aluminum wire).The fuse or circuit breaker feeding this circuit is rated for 20 amps.

On 2018-02-12 23:06:30.261456 by (mod) -

For a 20-Amp circuit use #12 copper wire (or #10 copper-clad aluminum wire).The fuse or circuit breaker feeding this circuit is rated for 20 amps.

On 2018-02-09 15:58:47.130686 by Jesse Bolado

What size to feed THHN wire to feed a 20 A receptacle

On 2017-11-24 00:39:58.858299 by (mod) -

Manny

#10 or possibly #8 on a longer run

On 2017-11-23 20:13:55.888726 by Manny

What grade of wiring would you use for from control panel to outlet for a 30 amp double oven maytag gemini electric range stove

On 2016-09-11 22:55:54.773359 by (mod) -

#8 is fine but see the warnings about box size and type as I explain above.

On 2016-09-11 22:22:06.887106 by (mod) -

Scott, to have space I've repeated your question and given a detailed answer at the end of the article above. Let me know what questions remain, and let me know who "it" says should be a #8 wire. Also, why 8/2? Are you not running a grounded circuit?

On 2016-09-11 21:51:44.678383 by Scott Davidson

I got the info off a rv web site yes using a 30 amp rv out let it did say for a 25' run you could use #10 but if it was over 25' from panel to outlet use #8 wire yes it is a special outlet for pluging in a rv i got at home depot Thank You

On 2016-09-11 by Scott Davidson

I would like to install a 30 amp 120 volt outlet to plug in my rv camper For the length of the run it says i should use number 8 /2 wire it is about 42 feet from panel to where plug would be installed is this correct Thanks Scott

On 2016-04-11 by (mod) -

15-Amp, #14 copper

On 2016-04-11 by Anonymous

What is minimum wire size for exterior receptacle

On 2015-11-02 by (mod) -

Good question, Bill. IF the fuse or circuit breaker is a 20-A unit then the wiring needs to be 12/2 to match.

But if your wiring is #14 copper (that's rated for 15-amp circuits) the right thing to do is to change the fuse or circuit breakers to match the #14 wire: make the breakers 15-amp units.

Separately it sounds as if you have loose or unsafe electrical wiring and connections that need to be tracked down.

On 2015-10-08 by bill

My mobile home has 12/2 15 amp receptacles.Is that ok? Should i replace them with 20 amp receptacles.

On 2015-08-2 by Steven C

I used some electrical wire I had in my workshop to add an electrical outlet in the floor. It will light up a lamp, but anything requiring more power (blender) won't work from this outlet. I am not sure of the size of the wire used. Is the size of this wire causing this issue?

 

Question: how is an electrical outlet wired to the electrical panel?

how do wire the outlet plug to the electrical panel - Anon

Reply:

Anon, the electrical circuit that powers an "outlet plug" or receptacle is connected, usually through building walls, ceilings, or floors, from the first receptacle in the particular series back to a fuse or circuit breaker connection in the electrical panel. The fuse or circuit breaker, by its connecting mount in the electrical panel, receives electrical power from the income electrical service.

Question: connecting 14-3 to 14-2 wires & to the junction box

How do you connect 14-3 to 14-2 to a junction box - Moe.

Reply:

Moe, twist on connectors are used to connect the incoming and outgoing hot, neutral, and ground wires, and a single pigtail length in that same twist-on connector can connect the ground to the local junction box.

Watch out: when mixing 14-3 and 14-2 wires on an electrical circuit.

If the 14-3 wires are the hot wires entering the box, and if only 14-2 is leaving the junction box, cap off the unused (typically the red) hot lead.

Do not just bond it together with the outgoing hot wire in the 14-2 group. Making that mistake would short two hot leads together, would be improper, unsafe, and a fire or shock risk.

I recently moved into a 3 1/4 story home, and I have a basement that I am trying to finish with drywall. The room is down to the studs and the electrical receptacles are about 4' up the wall. The Romex wiring is stapled, and there isn't enough wire to lower them.

It is way to much work for me to replace all of the downstairs wiring right to the breaker box, so I'm wondering if it is possible to add onto the existing wires and attach wire screws or marrets within the walls before I start adding drywall, or whether I should add some kind of junction box to contain the marreted wires in between.

My building code stipulations would differ in some cases because I live in Canada, but I just want to do the job right, and I do not want to take the chance of having any fire hazards, as I also have small children. - Dave 2/10/12

Reply: if you have to move an entire string of electrical receptacles complete re-wiring is faster and cheaper than adding a splice box for every device.

Dave,. you are correct to be careful about moving outlets or any other device when the existing wires are too short. The temptation is to just splice on an extension and bury that in the wall or ceiling: an illegal, improper, unsafe as well as really aggravating approach.

The proper approach is to add a junction box at each splice - we never splice 120/240V wires without including them in a box. You can reduce the wiring work a little by using plastic boxes instead of steel - avoiding having to also connect the box to the ground wire.

The proper approach also means that you don't then bury any of these splice-boxes in the walls either. Each box has to be brought to the surface and covered.

The result is a lot of work and expense and an ugly wall with an extra junction box and blind cover all along the wall over each of the now moved or lowered electrical receptacles.

Frankly I figure that especially as you've already got the wall open to the studs, if there are more than one or two receptacles to be moved you'll probably find it is actually much less total work to re-wire the entire circuit, allowing proper lengths of wires for each box.

You might carefully remove and re-route the existing wire lower in the wall or you might buy all new electrical wire - depending on the age and condition of the existing materials.

Watch out: when removing wire that appears to be in good condition, if you nick the insulation you've created a new hazard.

Question: armor around wire through concrete?

I am running a new 15A outlet into the back of a bookcase in a 50 year old house with updated electrical. The wire runs out the back of the retrofit box and down through the concrete foundation into the crawlspace to a wire I plan to splice into. Do I need to put armor around the wire run through the foundation? It goes through open air for about 2 feet and there is no way to secure it to anything.

Thanks!
Tom - 7/19/12

Reply:

You need to look at the type and rating of the electrical wire to determine if it is permitted to bury it in concrete or not.

Question: Am I allowed to add one more outlet onto an existing string?

I have an existing outlet being used for lamps I wanna run one more outlet shares from the hot on is it okay? - Phantom 113 8/1/12

Reply:

Usually, yes provided all safe and proper wiring code procedures are followed.

If the circuit is overloaded already, no.

If the circuit is knob and tube wiring, no - we don't extend knob and tube.

Question: is it legal to convert a split receptacle into two separate receptacles

Is it legal to change a spit receptacle to two separate receptacles? - Gord

Reply:

Gord,

unless I've missed something, sure.

You see this all the time. Instead of a single receptcale that has been split-wired to feed from two different circuits (usually using a common neutral and properly wired in the panel etc), you often see a 4" box with a pair of receptacles that side by side are run from different circuits instead of up and down different circuits in the same box.

Watch out about overloading the circuit however.

 

Question: I need to add a light, fan, and fan switch to an existing bath - I can't find where to kill the power

very informative article thumbs up . I have a question nevertheless:

I am renovating a customers bathroom and need to install another light as well as a fan witch requires a larger box to be installed in the wall.

When i checked the existing switch there was a black and a white wire on the switch and when i attempted to shut the power off to the light and switch at the panel there is no breaker that kills the power to the light

What is the likely cause of this and how do i fix this problem - Blinden 12/12/12

Reply:

Blinden,

It would be odd for a bath light circuit to be wired with no over current protection, and very dangerous too. Try each breaker in the panel in turn to find the one controlling the circuit.

As the switch is interrupting only the hot wire it is common practice to run a standard 2-wire line from the light to the switch. In meticulous electrical work the installer would wrap black tape near the ends of the white wire to indicate that in this use it is a hot lead not a neutral wire.

Depending on the light location, such as near a shower, it may need GFCI protection as well.

Question:

I have one line with power coming into a box that will have one two way switch, one three way switch and one power line exiting. Is it proper to splice the incoming black wire to make 3 black wires by pig tailing with wire connectors and doing the same for the white wire and ground? - is it ok? 12/13/12

Reply:

I'm sorry but I'm confused by the question. I think it's safe to say that in general it's common practice to use a twist-on connector to splice pigtails or individual wires at an individual hot or neutral wire where more connections are needfed than fit with the original wire.

Just watch out to avoid violating the space or number of connectors permitted in a junction box of the particular size you're working on.

Question: comment

Electrical wiring are the devices that are used to generate electricity. There are different types of electrical wiring that are usually vary according to three factors - purpose, quantity of electricity to be carried, and location. All the above three factors are really very important while doing electrical wiring. - Bella Cruse, Dublin electrical contractor

Reply:

Thanks Bella.

Question: which circuit is better to use when adding a closet light

If I want to add light to closet, which circuit is it better to pull from? I have access to 120 plug and switches in outside wall facing away from closet that could be pulled into closet. Also, can you help explain the two different wiring configurations on my non GFI plugs.

On two different plugs on different walls the plugs are 8 wire push in style (4 hot and 4 common), but the wiring config is different between the two plugs. One one all white and black are inserted in the bottom 4 connectors with tabs in place.

On another same style plug, one set of 4 wires (2 blk and 2 white) are inserted in bottom left row, and other set of 4 wires are inserted in opposite side top row. These plugs are not controlled by switches. Thank you. - Chris 12/30/12

Reply:

Chris,

In my OPINION, it's best to connect a closet light to the room lighting circuit if possible.

About your other question, I'm a little confused by the query, but in general, receptacles and switches often have more than one permittted connection point, such as under a screw terminal, on older devices via a back-wiring push-in connector (something we do not recommend using), or on newer devices a side-clamp operated by a screw.

In all events, regardless of which connection point you are using, receptacles and switches have a designated side or screw or connector set for the white (neutral wire) (typically the side that has a silver colored screw and that is marked NEUTRAL on the device) and for the black (hot wire) (typically the side that has a brass-colored screwe and is marked LINE or HOT or BLACKI).

Question: floor receptacle not working

(Aug 21, 2015) Steven C said:
I used some electrical wire I had in my workshop to add an electrical outlet in the floor.

It will light up a lamp, but anything requiring more power (blender) won't work from this outlet. I am not sure of the size of the wire used. Is the size of this wire causing this issue?

Reply:

Watch out: turn off the circuit and leave it off lest you cause a fire, shock, or injury. I can't know from your e-text if the wire is undersized or if there is damaged insulation or a current leak. It sounds unsafe to me.

Question: match the fuse or circuit breaker to fuse size?

(Oct 8, 2015) bill said:
My mobile home has 12/2 15 amp receptacles. Is that ok? Should i replace them with 20 amp receptacles.

Reply:

Good question, Bill. IF the fuse or circuit breaker is a 20-A unit then the wiring needs to be 12/2 to match.

But if your wiring is #14 copper (that's rated for 15-amp circuits) the right thing to do is to change the fuse or circuit breakers to match the #14 wire: make the breakers 15-amp units.

The electrical wire used for the receptacle circuit must be the proper type in size (thickness or gauge) and number of conductors for the ampacity of the electrical circuit

• The electrical circuit must be properly protected by the right fuse or circuit breaker
• For a 15-Amp circuit use #14 copper wire (or #12 copper-clad aluminum wire). The fuse or circuit breaker feeding this circuit is rated for 15 amps.
• For a 20-Amp circuit use #12 copper wire (or #10 copper-clad aluminum wire).The fuse or circuit breaker feeding this circuit is rated for 20 amps.
• For a 30-Amp circuit use #10 copper wire and a fuse or circuit breaker rated for 30 Amps.

Note1: it's safe and OK to use a smaller (lower ampacity) fuse or circuit breaker, such as a 15-amp fuse protecting a circuit wired with #12 copper wire.

Note2: it's generally safe and OK to use a larger size electrical wire, and a larger wire size may in fact be required for longer wiring runs.

Generally you want a 3% or less voltage drop across the wire from source to point of use. For the U.S., electrical wire sizes vs. circuit ampacity are given in National Electric Code Table 310-16.

Watch out: in complex circuits that have many connections within a single junction box you could get into trouble: the number of connections that are allowed within an individual junction box depends on the wire size and the size of the box itself. So increasing just the wire size could require that you use a larger electrical box.

...

Continue reading  at SIZE of WIRE REQUIRED for ELECTRICAL RECEPTACLES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

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• SE CABLE & BRANCH CIRCUIT WIRE SIZES vs AMPS for more wire size guidelines
• SPLICING ELECTRICAL WIRES
• UNDERGROUND SERVICE LATERALS for more wire sizing guidelines

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