Optimisers.

01How it works

An optimiser is a sealed unit about the size of a paperback, fixed to the frame behind each panel. It does for one panel what a string inverter's tracker does for a whole string: finds the point at which that panel gives its most, and holds it there.

The panels are still joined in a line and still run to one inverter on the wall. But each panel now arrives at that line already working at its own best, so the inverter's job is only to convert. SolarEdge is the system of this kind that we install.

02What shade does now

A shaded panel makes less. That's all. Its neighbours carry on at full output, because nothing ties their performance to its.

On a roof with a chimney, a vent pipe or a tree that reaches across in winter, that difference adds up across a year.

Each panel is judged on its own light, not on its neighbour's.

03Freedom in the design

Because each panel looks after itself, panels on different faces and at different pitches can share an inverter without holding each other back. A small face that would be awkward on a string system becomes usable.

For roofs made of several modest faces, which describes a great many Melbourne homes, this is often what makes a good-sized system possible at all.

04Seeing every panel

Optimisers report individually, so the app can show the roof panel by panel. A fault stops being a vague shortfall and becomes one panel out of step with the others, which makes it quick to find and quick to fix.

It's also simply interesting. You can watch the morning arrive across the east face and leave across the west.

05Safety on the roof

When the inverter is switched off, or the grid goes down, the optimisers reduce each panel's output to a very low voltage. The cable on the roof and through the house is no longer carrying the full voltage of the array, which matters to anyone who has to work near it.

06The trade

There are more parts, and they're on the roof. They're built for it and warranted for a long time, but a string system has nothing up there to replace.

The optimisers and the inverter are a matched set from one maker. That keeps the system coherent, and it means the choice is of a system, not of parts.