Micro-inverters or a string inverter — what changes between them?

A micro-inverter converts each panel independently, so a shaded module only costs its own output; a string inverter converts a whole series at once, more cheaply, and lets one shaded panel throttle its neighbours. Shade and roof shape decide more than price does.

Where the conversion from direct to alternating current happens is the architectural choice of a photovoltaic installation, and everything else follows it.

One converter or many

A string inverter takes a series of panels and converts the whole string at one operating point. Micro-inverters put a small converter behind every panel, so each one runs at its own best point and the string no longer exists as an electrical entity.

Why shade decides this

Panels in series share a current. A shadow on one module limits what the whole string can deliver, out of proportion to the area shaded. Per-panel conversion confines that loss to the shaded module, which is why chimneys, dormers and trees push installations towards it.

What the roof shape does

Panels facing different directions, or tilted differently, reach their best operating points at different times of day. A single string inverter has to compromise between them; per-panel electronics do not. A simple, uniform roof removes most of that argument.

The figures to compare

For any of them: the input voltage window, the maximum input current, the conversion efficiency across the load range rather than at its peak, and the grid standards named. Those four lines describe the unit; the architecture describes the roof.