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ITFrequently Asked Questions · Solar
What is the difference between string inverters and micro-inverters?
String inverters serve several strings of panels, while micro-inverters are installed on each panel for better performance in shaded conditions.
In a string inverter system the panels are wired in series, so the current of the whole string is limited by its weakest panel. If one panel is shaded by a chimney or a tree, the output of the entire string drops, not just that panel's. A micro-inverter converts DC to AC on each panel separately, with its own MPPT, so shading affects only that one panel.
A string inverter is usually the more economical option per kW, keeps the electronics in one place that is easy to reach for inspection or replacement, and suits simple, unshaded roofs. Micro-inverters offer per-panel monitoring, easy future expansion and low DC voltage on the roof, but they sit on the roof itself, where access for repairs is harder. There is also a middle ground: a string inverter with power optimizers fitted only to the panels that get shaded.
Before choosing, record how the roof is shaded at different times of day and year. On an open, single-plane roof a string inverter is usually enough; on roofs with several pitches, orientations or shadows, micro-inverters are worth considering.
