The reason different wire lengths bear different ratings is because the electrical resistance builds up as the cable gets longer. At that point, up-sizing the power cable will restore the voltage to its intended level.Acceptable Power Loss
Undersizing the wire size will result in excessive power (watts) being lost in the wires rather than delivered to the load (battery bank, inverter. Typically we recommend the power loss below 5%.Voltage Drop
A 5% voltage drop causes an approximate 10% loss in light output. Voltage drop causes a nearly proportional drop in light output. A voltage drop greater than 5% will reduce this necessary voltage difference, and can reduce charge current to the battery by a much greater percentage. Our general recommendation here is to size for a 2-3% voltage drop. If you think that the PV array may be expanded in the future, size the wire for future expansion.Don't choke the flow of power
On the other hand, installing too large a wire gauge doesn't really have a downside, but there is the potential for better performance. Obviously, there's no need to buy 2-gauge wiring when 10-gauge will do. That kind of overkill would be a waste of money. But if the calculator could lean either way between two sizes, going with the larger wire size would be the smart choice.
Calculate your Energy Requirements with a Renogy Solar Calculator
It’s very important to properly size your solar installation. We are happy to provide three distinct solar calculators to help you estimate your power project requirements: a solar sizing, cable gauge, and battery interconnect calculator.
The Solar Sizing Calculator allows you to input information about your lifestyle to help you decide on your solar panel requirements. You’ll just need to know what total watts your electronics will consume, how long you plan on running the devices, your charge controller efficiency, and the average sun hours per day. The solar sizing calculator will then be able to tell you the minimum and recommended system size, as well as the recommended battery output.
The Solar Cable Gauge Calculator is designed to provide estimates for wire gauge size to determine your need for cables. This is crucial to building a safe and efficient system to meet your energy needs.
The Battery Interconnect Calculator helps you estimate your system’s requirements for interconnect cables based on inverter voltage, battery voltage, how many batteries you are using, and the number of strings in parallel.
Using our solar calculators will give you an accurate understanding of your system’s specific needs, which in turn will give you a better idea of the costs, requirements, and equipment needs for your solar system.