Solar Panel Matcher

The Solar Panel Matcher checks each solar panel in our database against your device's electrical limits — maximum input voltage, maximum input current, and rated wattage. For every panel, the tool calculates valid wiring configurations including series strings, parallel connections, and series-parallel combinations.

Critically, the matcher accounts for temperature effects on voltage. Solar panel voltage increases as temperature drops, which means a panel that looks safe at room temperature could exceed your controller's voltage limit on a cold winter morning. By entering your local cold-temperature extreme, the tool calculates the worst-case open circuit voltage (Voc) for each panel and only recommends configurations that remain within safe limits.

Solar panel voltage increases as temperature drops. This is a fundamental property of silicon photovoltaic cells — lower temperatures reduce the thermal agitation of electrons, which raises the bandgap voltage. Every panel datasheet lists a Temperature Coefficient of Voc (beta), typically around -0.25% to -0.35% per degree Celsius.

For example, consider a panel with a Voc of 46.6V and a temperature coefficient of -0.27%/°C. At standard test conditions (25°C), the Voc is 46.6V. But at -25°C — a 50-degree drop — the voltage increases by about 13.5%, giving a cold-weather Voc of approximately 52.9V. Two of these panels wired in series would produce about 105.8V, which could exceed the 100V input limit on many charge controllers.

This cold-temperature voltage rise is the number one cause of charge controller damage in cold climates. The Solar Panel Matcher uses your local temperature data to calculate these worst-case voltages and prevent dangerous configurations.

Series Wiring

In a series connection, panel voltages add together while current stays the same. Two 40V / 10A panels wired in series produce 80V at 10A. Series wiring is best for MPPT charge controllers (which can step down high voltage efficiently), long wire runs (higher voltage means less current and lower wire losses), and installations with no shading issues.

Parallel Wiring

In a parallel connection, panel currents add together while voltage stays the same. Two 40V / 10A panels wired in parallel produce 40V at 20A. Parallel wiring is best for PWM charge controllers (which require panel voltage close to battery voltage), partially shaded installations (shade on one panel does not drag down the others), and short wire runs where higher current is acceptable.

Series-Parallel Wiring

Series-parallel combines both approaches: panels are wired into series strings, then the strings are connected in parallel. This balances voltage and current to stay within controller limits while maximizing total array power. It is the standard configuration for larger solar arrays with four or more panels.

When wiring solar panels in parallel, fusing protects against reverse current flow that can damage panels in a fault condition. The National Electrical Code (NEC 690.9) governs fusing requirements for photovoltaic systems:

• 2 parallel strings: Fuses are recommended but not always required, depending on the panel's series fuse rating.
• 3 or more parallel strings: Fuses are mandatory per NEC 690.9. Each string must have its own overcurrent protection device.

Fuse sizing follows a standard formula: multiply the short-circuit current (Isc) of a single string by 1.56 (which accounts for the NEC 1.25 safety factor applied twice — once for continuous current and once for panel output tolerance). Always use DC-rated fuses or breakers, as AC-rated devices cannot safely interrupt direct current arcs.

For proper wire sizing between your panels and charge controller, use our Wire Size Calculator.