String Inverter

A string inverter is a centralized device that converts the DC electricity produced by a series-connected string of solar panels into AC electricity for your home's electrical system or the utility grid. It is the most common and cost-effective inverter architecture for residential and commercial grid-tied solar installations.

In a string inverter system, multiple panels are wired in series to create high-voltage DC strings (typically 200-600V for residential, up to 1,000V or 1,500V for commercial). These strings feed into a single inverter that performs MPPT and DC-to-AC conversion for the entire array. One inverter handles all the panels — keeping equipment costs low and maintenance simple.

The primary limitation of string inverters is their response to partial shading. Because panels in a series string share the same current, shading on any single panel reduces the output of the entire string. The inverter's MPPT algorithm can only optimize for one power point per string, so localized shading drags down all connected panels to some degree.

Modern string inverters mitigate this with dual or triple MPPT inputs, allowing panels facing different directions or experiencing different shade conditions to be grouped on separate MPPT channels. High-end string inverters from brands like SMA, Fronius, SolarEdge (with optimizers), and Enphase's competitor models offer 97-99% peak conversion efficiency.

String inverters are best suited for installations with consistent sun exposure across all panels — south-facing roofs without obstructions, ground-mount arrays, and carports. For roofs with complex geometry, multiple orientations, or significant shade, microinverters or power optimizers may deliver better total energy harvest.