NEC Ground Wire Size Chart: What Size Ground Wire Do You Need + Amps? (2024)

For every wire, you will need a ground wire. As you may know, the ground wire doesn’t have to be as big as the main wire. Example: 1 AWG copper wire doesn’t require a 1 AWG copper ground wire. It requires a 6 AWG copper ground wire. A ground wire size chart that follows will tell you exactly the size of the grounding conductor you need.

Now, it’s important to understand that you cannot go wrong with a bigger-than-required ground wire. A big ground wire is just overkill that will cost you more. That’s it.

NEC Ground Wire Size Chart: What Size Ground Wire Do You Need + Amps? (1)

To find the most optimum ground wire size, you have to consult the ‘NEC Grounding Conduction Size Chart’.

What section of the NEC covers grounding?

National Electrical Code (NEC) covers the sizes of ground wires in Article 250, Table 250.66 titled ‘Grounding Electrode Conductor For Alternativing Current Systems’. This 250.66 NEC table is also known as the equipment grounding conductor size chart.

Since it’s not all that easy to get hands on these new 2020 NEC guidelines, we are sharing this chart below. You will see two charts:

1st chart covers the size of copper wires (from 8 AWG to 2000 kcmil) and their corresponding copper ground wires.
2nd chart covers the size of aluminum wires (from 6 AWG to 2000 kcmil) and their corresponding aluminum ground wires.

To figure out what size ground wire you need, just consult these two charts. Below each chart, we also list some examples of ground wire sizing choices:

Copper Ground Wire Size Chart (Copper Grounding Conductor Size Chart)

Size Of Copper Wire (AWG or kcmil):	Copper Grounding Electrode Conductor Size (AWG or kcmil):	Amps:
8 AWG Copper Wire	8 AWG Copper Ground Wire	50 Amps
6 AWG Copper Wire	8 AWG Copper Ground Wire	65 Amps
4 AWG Copper Wire	8 AWG Copper Ground Wire	85 Amps
3 AWG Copper Wire	8 AWG Copper Ground Wire	100 Amps
2 AWG Copper Wire	8 AWG Copper Ground Wire	115 Amps
1 AWG Copper Wire	6 AWG Copper Ground Wire	130 Amps
0 (1/0) AWG Copper Wire	6 AWG Copper Ground Wire	150 Amps
00 (2/0) AWG Copper Wire	4 AWG Copper Ground Wire	175 Amps
000 (3/0) AWG Copper Wire	4 AWG Copper Ground Wire	200 Amps
0000 (4/0) AWG Copper Wire	2 AWG Copper Ground Wire	230 Amps
250 kcmil Copper Wire	2 AWG Copper Ground Wire	255 Amps
300 kcmil Copper Wire	2 AWG Copper Ground Wire	285 Amps
350 kcmil Copper Wire	2 AWG Copper Ground Wire	310 Amps
400 kcmil Copper Wire	0 (1/0) AWG Copper Ground Wire	335 Amps
500 kcmil Copper Wire	0 (1/0) AWG Copper Ground Wire	380 Amps
600 kcmil Copper Wire	0 (1/0) AWG Copper Ground Wire	420 Amps
700 kcmil Copper Wire	00 (2/0) AWG Copper Ground Wire	460 Amps
750 kcmil Copper Wire	00 (2/0) AWG Copper Ground Wire	475 Amps
800 kcmil Copper Wire	00 (2/0) AWG Copper Ground Wire	490 Amps
900 kcmil Copper Wire	00 (2/0) AWG Copper Ground Wire	520 Amps
1000 kcmil Copper Wire	00 (2/0) AWG Copper Ground Wire	545 Amps
1250 kcmil Copper Wire	000 (3/0) AWG Copper Ground Wire	590 Amps
1500 kcmil Copper Wire	000 (3/0) AWG Copper Ground Wire	625 Amps
1750 kcmil Copper Wire	000 (3/0) AWG Copper Ground Wire	650 Amps
2000 kcmil Copper Wire	000 (3/0) AWG Copper Ground Wire	665 Amps

Let’s look at two examples:

What size ground wire do I need for a 3 AWG wire?

3 AWG wire has an ampacity of 100A at a median 75°C (167°C) temperature. This is also why people confuse it with being a 100 amp wire. You can check what size wire you need for 100 amps here.

To figure out the size of the ground wire, you consult the copper grounding conductor size chart, and you see that you need an 8 AWG copper ground wire for 3 AWG copper wire (for 100 amps, you can use 8 AWG copper ground wire). Now, there is nothing wrong if you use a 6 AWG or even 4 AWG ground wire; it will do the same job, it will just cost more.

What size ground wire do I need for 250 kcmil wire?

250 kcmil copper wire has a 255A ampacity at a median conductor temperature. If you apply the NEC 80% rule, 250 kcmil wire can handle up to 204 amps. That’s why it is considered a 200 amp wire. Basically, we are trying to answer what ground wire do you need for 200 amp service.

If you consult the copper ground wire size chart above, you can see that you will need a 2 AWG copper ground wire to adequately ground a 250 kcmil wire. Basically, you need a 2 AWG copper ground wire for a 200 amp service.

Let’s look at the NEC recommendations for aluminum wires as well:

Aluminum Ground Wire Size Chart (Aluminum Grounding Conductor Size Chart)

Size Of Aluminum Wire (AWG or kcmil):	Aluminum Grounding Electrode Conductor Size (AWG or kcmil):	Amps:
6 AWG Aluminum Wire	6 AWG Aluminum Ground Wire	60 Amps
4 AWG Aluminum Wire	6 AWG Aluminum Ground Wire	75 Amps
3 AWG Aluminum Wire	6 AWG Aluminum Ground Wire	85 Amps
2 AWG Aluminum Wire	6 AWG Aluminum Ground Wire	100 Amps
1 AWG Aluminum Wire	4 AWG Aluminum Ground Wire	115 Amps
0 (1/0) AWG Aluminum Wire	4 AWG Aluminum Ground Wire	135 Amps
00 (2/0) AWG Aluminum Wire	2 AWG Aluminum Ground Wire	150 Amps
000 (3/0) AWG Aluminum Wire	2 AWG Aluminum Ground Wire	175 Amps
0000 (4/0) AWG Aluminum Wire	0 (1/0) AWG Aluminum Ground Wire	205 Amps
250 kcmil Aluminum Wire	0 (1/0) AWG Aluminum Ground Wire	230 Amps
300 kcmil Aluminum Wire	0 (1/0) AWG Aluminum Ground Wire	255 Amps
350 kcmil Aluminum Wire	0 (1/0) AWG Aluminum Ground Wire	280 Amps
400 kcmil Aluminum Wire	000 (3/0) AWG Aluminum Ground Wire	305 Amps
500 kcmil Aluminum Wire	000 (3/0) AWG Aluminum Ground Wire	350 Amps
600 kcmil Aluminum Wire	000 (3/0) AWG Aluminum Ground Wire	385 Amps
700 kcmil Aluminum Wire	0000 (4/0) AWG Aluminum Ground Wire	420 Amps
750 kcmil Aluminum Wire	0000 (4/0) AWG Aluminum Ground Wire	435 Amps
800 kcmil Aluminum Wire	0000 (4/0) AWG Aluminum Ground Wire	450 Amps
900 kcmil Aluminum Wire	0000 (4/0) AWG Aluminum Ground Wire	480 Amps
1000 kcmil Aluminum Wire	0000 (4/0) AWG Aluminum Ground Wire	500 Amps
1250 kcmil Aluminum Wire	250 kcmil Aluminum Ground Wire	545 Amps
1500 kcmil Aluminum Wire	250 kcmil Aluminum Ground Wire	585 Amps
1750 kcmil Aluminum Wire	250 kcmil Aluminum Ground Wire	615 Amps
2000 kcmil Aluminum Wire	250 kcmil Aluminum Ground Wire	630 Amps

Compared to copper wires, aluminum wires have about 39% lower conductivity. That’s why you have to use different grounding wires for aluminum wires.

Let’s look at two examples of aluminum ground wires:

How big aluminum ground wire do you need for a 00 AWG aluminum wire?

Just check the aluminum ground wire size table above and you will see that you need a 2 AWG aluminum ground wire for 00 AWG aluminum wire grounding.

What size ground wire do I need for 500 kcmil aluminum wire?

Same thing. Check the NEC equipment grounding conductor chart for aluminum wires above, and you will see that you need a 000 AWG aluminum ground wire for adequately grounding a 500 kcmil aluminum wire.

With these two charts, you can pretty much figure out how big equipment grounding conductors you need. If you have any questions, just use the comments below and we’ll try to help you out.

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FAQs

NEC Ground Wire Size Chart: What Size Ground Wire Do You Need + Amps? ›

There should always be zero amps on the ground wire. On a 230 Volt item the neutral wire may not carry any amps, unless there is a control or some 110 v component, like a control panel. Often the white wire is used as the second hot leg instead of as a neutral.

How far apart should ground rods be? ›

As far as spacing of the grounding electrodes goes, NEC 250.53 (B) requires a minimum of 6-ft between electrodes.

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Can you use 3,0 copper wire for 200 amp service? ›

When installing a 200 Amp service, you will need at least 3/0 AWG copper wire or 4/0 AWG aluminum or aluminum copper-clad wire. Allowable ampacity of 3/0 copper wire is 225 Amp, while the allowable ampacity of 4/0 aluminum wire is 205 Amp.

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What is the minimum ground wire size for NEC? ›

Increases in equipment grounding conductor size to address voltage drop considerations are not required. An equipment grounding conductor can never be smaller than 14 AWG. Below is a preview of the NEC^®. See the actual NEC^® text at NFPA.ORG for the complete code section.

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What is the best gauge for ground wire? ›

The ground wire, often referred to as the grounding electrode conductor, is the link between the ground rod and the service ground connection. Ground wires for residences typically are made of copper and are #6 (6 AWG) or larger. For 200 Amp services, a #4 grounding electrode conductor (ground wire) is required.

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Does ground wire have to be the same size as the power wire? ›

The ground wire can always be one wire size smaller than the main & neutral conductors. There is also locations & applications that the ground can be much smaller, consult the national electrical code for specifics.

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Does ground wire need to be the same size as power? ›

The current is equal at all points in a series circuit (Kirchoff's current law). The same amount of current therefore flows through the positive and ground wires. Both wires need to be at least thick enough to handle the current the circuit draws, but they can have different thicknesses.

Why is there current on the ground wire? ›

If an electrical fault occurs, the excess current will be directed to the ground wire and into the earth, rather than building up in the electrical system and potentially starting a fire.

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