String, optimiser, micro.

01The job

Panels make direct current. Your home runs on alternating current. Something has to convert one to the other and, while it's at it, get the most out of every panel. There are three ways to arrange that, and the difference between them is where the electronics sit.

02String inverters

Panels are wired one after another into a string, and each string runs down to a single inverter on the wall. It's the simplest arrangement, with the fewest parts on the roof and everything that might need attention within reach.

The trade is that panels on a string work together. If one is shaded, the others on that string are held back with it. On a clear roof with one or two faces that hardly matters, and modern inverters can run separate faces as separate strings. On a clear roof, a string system is hard to beat.

03Optimisers

An optimiser is a small unit fixed behind each panel. It lets that panel work at its own best, whatever its neighbours are doing, and passes the result down to one inverter on the wall. SolarEdge is the system of this kind that we install.

A shaded panel then costs you that panel's output and nothing more. You also get monitoring for each panel, so a fault shows up as one panel out of step, not as a vague shortfall across the roof. The cost is more components on the roof.

The question isn't which technology is best. It's which one your roof needs.

04Microinverters

A microinverter is a complete small inverter under each panel. The conversion happens on the roof, and alternating current comes down the cable. Every panel is fully independent, and there is no central inverter on the wall.

As with optimisers, shade on one panel stays with that panel, and each is monitored on its own. The electronics are all on the roof, which is where they're hardest to reach, and a battery is added on the home's side with an inverter of its own.

05Which suits which roof

A clear roof with one or two large faces is well served by a string inverter. A roof with a chimney, a tree, dormer windows or panels spread over several small faces usually wants panel-level electronics, so each panel can be judged on its own.

The less obvious cases are the ones worth a proper look: a roof that's clear in summer and shaded in winter, or one where a small awkward face would make a useful difference to your afternoons.

06Where the battery fits

If a battery is part of the plan, now or later, it shapes the choice. A hybrid inverter runs panels and a battery together through one unit. Adding a battery to a system that wasn't designed for one is possible, but it usually means a second inverter.

So it's worth saying at the start whether a battery is on your mind, even if it's a few years off.