Conductor size

A comparison of standard mm² wire sizes and standard AWG wire sizes. AWG decreases as wire size increases, mm² increases as wire size increases.

Wires come in standard sizes depending upon the location. The proper wire size for a particular circuit depends on two important considerations:

1. The amount of current that they can safely carry given the conditions in which they will be used.
2. The amount of voltage that will be lost under operation, which is called voltage drop

The wires for an off-grid system must will be sized and selected based upon the load evaluation and the physical evaluation for a particular site. This process must be done in conjunction with the sizing and selection of the overcurrent protection device - see Wire and overcurrent protection sizing and selection for more information.

The two most common standards for wire size are American Wire Gauge (AWG) and mm². These two systems are not directly equivalent. The table below shows wire sizes in AWG and mm² with the allowable current when there are 1-3 copper conductors in conduit with a 30°C ambient temperature.

			60°C	75°C	90°C
AWG size	Area (mm²)	Metric equivalent (mm²)	Types TW, UF	Types RHW, THHW, THW, THWN, XHHW, USE, ZW	Types TBS, SA, SIS, FEP, FEPB, MI, RHH, RHW-2, THHN, THHW, THW-2, THWN-2, USE-2, XHH, XHHW, XHHW-2, ZW-2
14	2.08 mm²	2.5 mm²	15 A	20 A	25 A
12	3.31 mm²	4 mm²	20 A	25 A	30 A
10	5.26 mm²	6 mm²	30 A	35 A	40 A
8	8.37 mm²	10 mm²	40 A	50 A	55 A
6	13.3 mm²	16 mm²	55 A	65 A	75 A
4	21.2 mm²	25 mm²	70 A	85 A	95 A
3	26.7 mm²	—	85 A	100 A	110 A
2	33.6 mm²	35 mm²	95 A	115 A	130 A
1	42.4 mm²	50 mm²	110 A	130 A	150 A
1/0	53.5 mm²	—	125 A	150 A	170 A
2/0	67.4 mm²	70 mm²	145 A	175 A	195 A
3/0	85 mm²	95 mm²	165 A	200 A	225 A
4/0	107 mm²	120 mm²	195 A	230 A	260 A

Cable size

Cables are typically designed to contain all of the wires that are needed for a particular circuit. Therefore there are many different configurations of cable that vary based upon the size of the wires, the number of wires, and the color of the wires. Cables will be labeled with the size of the current carrying conductors and the quantity. For example a cable with three 12 AWG wires will be labeled "12/3". A cable with three 2.5mm² will be labeled "2.5mm²/3" or "2.5mm² three core". Equipment grounding conductors (EGCs) are generally excluded from the count of conductors and should be specified separately.