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Thad's Tip: Calculate Wire Gauge for Your Off Grid Water System

Click here to view, print, or download How to Use the Voltage Drop Index Method to Calculate Wire Gauge For Your Off Grid Water System v2m.pdf

Choosing the best wire gauge for the cables in your off grid water system can be confusing. This calculation takes the guesswork out of figuring out the right wire size for your solar water pump setup. You can use this for any low voltage DC wiring in your remote solar power system.


Solar Panels Amps x One-Way Distance =VDI
System Voltage x 2


VDI 1 2 3 5 8 12 20 34 49 62 78 99
Gauge 16 14 12 10 8 6 4 2 1/0 2/0 3/0 4/0


●    5 amps from solar panels
●    100 feet from solar panels to pump
●    24 volts, two solar panels wired in series
5 x 100  = (500 divided by 48), which equals 10.4
24 x 2

Nearest gauge to 10.4 VDI is in between 6 and 8, so you go with the larger size gauge and use a 6 gauge wire.

Wire diameter (size) gets smaller as the gauge gets larger.


Click here to find out more about Solar Water Pumps