How do you select the appropriate wire gauge for a solar panel system?

1 Current and voltage

The first step to select the wire gauge is to determine the maximum current and voltage that your solar panel system will produce. Current is measured in amps (A) and voltage in volts (V). You can find these values on the specifications of your solar panels, charge controller, inverter, and battery. The current and voltage will vary depending on the configuration of your system, such as series, parallel, or hybrid. Generally, series connections increase the voltage but keep the current constant, while parallel connections increase the current but keep the voltage constant.

2 Length and temperature

The second step to select the wire gauge is to measure the length and estimate the temperature of the wires that will connect your solar panel system components. Length is measured in feet (ft) or meters (m) and temperature in degrees Fahrenheit (F) or Celsius (C). The longer and hotter the wires are, the more resistance they will have, which means more power loss and heat generation. You want to minimize the length and temperature of the wires as much as possible, or use larger wire gauges to compensate for the increased resistance.

3 Wire gauge chart

The third step to select the wire gauge is to use a wire gauge chart that shows the maximum current capacity of different wire sizes for different lengths and temperatures. You can find online or offline wire gauge charts that are specific for solar panel systems, or use a general one that follows the American Wire Gauge (AWG) standard. The wire gauge chart will tell you the minimum wire size that can safely and efficiently handle the current and voltage of your solar panel system for a given length and temperature. For example, if your system produces 20 A and 48 V, and your wire length is 50 ft and temperature is 90 F, you will need at least a 10 AWG wire.

4 Safety factor

The fourth and final step to select the wire gauge is to add a safety factor to your calculation. A safety factor is a percentage that you multiply by the current or voltage of your system to account for possible fluctuations, surges, or spikes that may occur due to environmental or operational conditions. A common safety factor for solar panel systems is 25%, which means you multiply the current or voltage by 1.25 and then use the wire gauge chart to find the appropriate wire size. For example, if your system produces 20 A and 48 V, you will multiply them by 1.25 and get 25 A and 60 V, which will require a 8 AWG wire.

5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?