String Inverter

How a string inverter works

Solar panels produce DC power. Your home runs on AC power. The inverter is the conversion unit in the middle. In a string inverter system, panels are wired together in series - a “string” - where the DC output of each panel feeds into the next. All the DC power from the string flows into a single inverter box that converts it to 240V AC.

The inverter sits between the solar array and the switchboard, typically mounted on an exterior wall of the house or in the garage. Most residential installations use a single string inverter, though larger systems may use two or a dual-MPPT inverter to handle panels on different roof orientations.

The shading problem

The weakness of string inverters is their Achilles heel: because all panels in a string are wired in series, the weakest panel limits the output of the entire string. If one panel is shaded - by a chimney, an antenna, bird droppings, or leaves - the whole string drops to that panel’s reduced output.

This is analogous to Christmas lights wired in series: one failed bulb kills the whole string.

String inverters with optimisers

Power optimisers are module-level electronics added to each panel to mitigate this problem. They condition each panel’s output independently before feeding into the string inverter, allowing the other panels to operate at full power when one is shaded or underperforming.

SolarEdge is the dominant manufacturer of this architecture in Australia. It’s more expensive than a plain string inverter but cheaper than a full microinverter system, and it adds per-panel monitoring so you can see exactly which panels are underperforming and why.

The dominant technology in Australia

String inverters remain the most common residential solar inverter in Australia for good reason: they’re cost-effective, proven, well-supported, and efficient (typically 97–98% conversion efficiency). In unshaded situations - a clear north-facing roof with no obstructions - a quality string inverter from Fronius, SMA, Huawei, or Sungrow performs as well as any more complex alternative.

The brands on the CEC’s approved inverter list include both locally supported and grey-market options. Sticking to brands with established Australian service networks (Fronius, SMA, Huawei, Goodwe, Sungrow) reduces the risk of warranty claims being difficult to pursue.