While there is no maximum cable length for a photovoltaic panel, installers should consider the drop-off in voltage as cable length increases, which entails running a cable with a greater diameter. (See our solar cable size calculator, below. ) How Far Can You Run Solar. When the length of the cable is long for a certain current flow and wire size, the electrical voltage that will reach the load, whether it is charge controller or inverters, will be less, and the device may not work to charge the batteries properly, as the charge controller is not designed to. A Solar Voltage Drop Calculator is a specialized tool that helps you measure how much voltage is lost as electricity travels from your solar panels to your charge controller, inverter, or battery bank. Selecting the right cable involves balancing three main factors: the current it will carry, the length of the cable run, and the acceptable voltage drop. When it comes to solar installations, the wiring may seem like a minor detail, but it plays a. Selecting the appropriate length of DC solar cables requires a balance between minimizing energy losses, adhering to safety standards, and optimizing installation costs.