String Inverter
A central inverter that converts DC electricity from a series-wired string of panels — cost-effective but limited by the worst-performing panel in the string.
In a string inverter setup, solar panels are wired in series (strings), and all DC power flows to one central inverter that converts it to AC. String inverters are the most cost-effective option and have been the industry standard for decades. Their efficiency (97–99%) and reliability are well-proven, with 10–15 year lifespans.
The fundamental limitation: because panels in a string are wired in series, current through the string is limited to the output of the weakest panel. A single shaded, dirty, or underperforming panel constrains the entire string — a "Christmas light effect." In practice, this means even partial shading of 10–15% of a roof area can reduce total system output by 30–50%.
String inverters are appropriate for simple, unobstructed south-facing roofs with minimal shading. For complex roof shapes, multiple roof orientations, or trees/chimneys casting shadows, microinverters or power optimizers are better choices despite their higher cost. Some string inverters include built-in monitoring; others require additional equipment.
Real-World Example
The south-facing 12-panel string performed flawlessly until a neighbor's new addition shaded three panels each afternoon; because all 12 panels shared a string inverter, the three shaded panels reduced the entire array's afternoon output by 60%.