Voltage Loss Tables for AWG Wire

What Gauge AWG Wire to Use for Solar Electric Systems

Includes 12, 24, and 120-volt charts and a metric to AWG size conversion table.

This is a five percent table which means at these amperage ratings at the listed distances, 5% of the power would be lost to resistance. Five percent is normally acceptable in low voltage systems, but if you want a 2% figure, divide the given distances by 2.5. For a 10% loss multiply the distance by 2. For distances at 48 volts, double the 24-volt distances for a 5 percent loss figure. For 240 volt 5% loss, double the 120-volt distances. These distances include the NEC requirement for current oversizing of 25%.

Example: For a pump drawing 9 amperes at 24 volts, located 88 feet from the battery bank: look at the center table for 24 volts. In the far left column find the next number higher than 9 (which is 10) and follow that line across the table until you find a distance figure greater than 88. At the top of the column find the gauge of wire (#6) that should be used. This method ensures that wire losses are kept to an acceptable level without spending too much money on extra-heavy cable. Using a heavier wire than indicated, however, will result in even higher efficiencies and we do sometimes invest in the next larger gauge. Wire can get expensive, and it may not be worth the money to get that last 1% if you have to go to a much larger wire size.

Some of the newer grid tie systems inverters, such as the Sunny Boy, use up to 600 volts DC. Generally in these systems loss in wire is nothing to worry about. HOWEVER - you will have to be more careful about selecting and installing the wiring - high voltage DC is not something you want to do a 2nd rate wiring job on. Make sure the insulation is rated for 600 volts, and that there is no damage to the wire or insulation.

All distances are in FEET

Do not use any wire sizes that might fall into the red zone - this would exceed the amperage rating of the wire and it may overheat and burn.

120 Volts AC or DC Chart

Amps in Wire	Watts at 120V	#14	#12	#10	#8	#6	#4	#2	1/0	2/0	3/0
2	240	422	656
4	480	187	328	516
6	720	141	225	328	562
8	960	103	159	272	422	666
10	1200	84	131	216	337	534
15	1800	56	84	131	225	356	562
20	2400		65	103	168	272	422	675
25	3000			84	131	216	337	543
30	3600			65.63	112	178	281	450	722
40	4800				84	131	216	337	543	675
50	6000				67	103	171	272	431	543	684

24 Volts DC Chart

Amps in Wire	Watts at 24V	#14	#12	#10	#8	#6	#4	#2	1/0	2/0	3/0
1	24	169	262	412	675
2	48	84	131	207	337	532
4	96	37	66	103	169	267
6	144	28	45	66	112	178	282
8	192	21	32	54	84	133	216
10	240	17	26	43	67	107	169	270
15	360	11	17	26	45	71	112	180	289
20	480		13	21	37	54	84	135	217	270	343
25	600			17	26	43	67	108	172	217	274
30	720			13	22	36	56	90	144	180	228
40	960				17	26	43	67	108	135	171
50	1200				13	21	34	54	86	108	137

12 Volts DC Chart

Amps in Wire	Watts at 12V	#14	#12	#10	#8	#6	#4	#2	1/0	2/0	3/0
1	12	84	131	206	337	532
2	24	42	66	103	168	266	432	675
4	48	18	33	52	84	133	216	337	543	675
6	72	14	22	33	56	89	141	225	360	450	570
8	96	10	16	27	42	66	108	168	272	338	427
10	120	8.5	13	22	33	53	84	135	218	270	342
15	180	6	8.5	13	22	35	56	90	144	180	228
20	240		6.6	10	16	27	42	67	108	135	171
25	300			8	13	22	33	54	86	108	137
30	360			6.6	11	18	28	45	72	90	114
40	480				8	13	21	33	54	67	85

These are one-way distances, measured from point A to point B. The out and back nature of electrical circuits has already been included. For PV arrays, figure the entire run, from the panels to the charge controller to the batteries

Cross Reference of AWG (American Wire Gauge) Sizes to Metric (mm)

AWG	mm²	AWG	mm²	AWG	mm²	AWG	mm²
30	0.05	18	0.75	6	16	4/0	120
28	0.08	17	1.0	4	25	300MCM	150
26	0.14	16	1.5	2	35	350MCM	185
24	0.25	14	2.5	1	50	500MCM	240
22	0.34	12	4.0	1/0	55	600MCM	300
21	0.38	10	6.0	2/0	70	750MCM	400
20	0.50	8	10	3/0	95	1000MCM	500

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