Series Wiring

Series wiring connects solar panels end-to-end by linking the positive terminal of one panel to the negative terminal of the next, forming a chain called a string. In a series connection, the voltages of all panels add together while the current remains the same as a single panel.

For example, four 400W panels in series, each with a Vmp of 34V and Imp of 11.8A, produce a combined 136V at 11.8A (136 × 11.8 = 1,605W). The higher voltage allows the use of smaller wire gauges for the same power level, since power loss in wiring is proportional to current squared (I²R losses).

Series wiring is the standard configuration for grid-tied string inverters and MPPT charge controllers, which are designed to accept high-voltage, lower-current inputs and convert them to the appropriate output. MPPT controllers particularly benefit from series wiring because the higher input voltage gives them more conversion headroom.

The main disadvantage of series wiring is shade sensitivity. In a series string, the panel producing the least current limits the entire string's current output. If one panel in a four-panel string is partially shaded and produces only 6A, the entire string drops to 6A regardless of the other panels receiving full sun. Bypass diodes in each panel mitigate this to some extent but do not eliminate it entirely.

Series wiring is combined with parallel wiring in larger systems to build arrays that balance voltage and current for optimal equipment compatibility.