The short answer: with no shade and a single orientation, a string inverter is usually the best option. Less electronics on the roof, fewer points of failure and a lower cost. Optimisers and microinverters pay off when there is shade or a complicated roof. Here is the full reasoning, the same one we apply in every solar installation built on a proper study.
All three do the same thing in the end: convert the panels' direct current into the alternating current your house uses. They differ in where the electronics live and in how much each panel depends on the others. That is where their advantages and their drawbacks come from.
Panels are wired in series, like a row, to a single inverter mounted on a wall, usually in the garage or next to your consumer unit.
All the power electronics live downstairs, out of the sun. On the roof there are only panels and cable. It is the option with the fewest devices and the most economical.
Each panel carries a small box underneath that lets it work at its best even when another panel in the row is shaded. There is still a central inverter.
They break the rule of the row: a shaded panel no longer holds the others back. They add panel-by-panel monitoring, and they also add electronics on the roof.
Each panel has its own small inverter on the roof. There is no central inverter: each panel works and is measured on its own.
No panel depends on another and there is no single point of failure. It is the option with the most electronics on the roof and the highest upfront cost.
If your roof has no shade and every panel faces the same way, a string inverter is hard to beat: it is the simplest option, the cheapest, and the one that puts the fewest devices out in the sun. In engineering, every device you do not install is a device that never fails.
Its limit is the series. Panels wired in a row perform at the pace of the worst one. A chimney shading a single panel mid-afternoon slows the whole row. That is why string needs a clean roof: without that condition, it stops being the simple option and becomes the wrong one.
Its maintenance advantage is real. The electronics work on a wall, in the shade and within reach. The day the inverter needs replacing, and over the years it usually does, the swap happens downstairs, with no scaffolding and no panels lifted. That 25-year sum matters as much as the day-one price.
They pay off when the roof breaks the string conditions: shade that comes and goes through the day, panels split across two or more orientations, or rows that cannot be equal. Then the extra electronics stop being a luxury and start paying for themselves with the production they rescue.
Optimisers: the middle ground. They keep a central inverter and free each panel from the tyranny of the row. They are the usual answer to partial shade, the neighbour's chimney or a roof with two faces. In exchange, they put electronics up on the roof, and the central inverter remains a single point of failure.
Microinverters: full independence. Each panel works on its own, there is no single point of failure and the installation can grow panel by panel if you ever extend it. They are the answer to genuinely complicated roofs: several orientations, difficult shade, irregular spaces. They are also the most expensive option, and proposing them where they are not needed means charging you for electronics you do not need.
What you gain in both cases: seeing every panel. With optimisers and microinverters, production is measured panel by panel. A dirty or faulty panel shows up on its own, without waiting for the bill to creep up. With string you see the installation's total, which is usually enough for a uniform roof. We check what your installation produces every day whichever electronics you choose.
All the electronics you put on the roof work in the sun, at higher temperatures and harder to reach than the ones on the wall. More devices mean more possible faults over 25 years, and every replacement up there means climbing onto the roof and lifting a panel. That is a cost too, even if it never shows in the first figure.
A long warranty does not cover everything. Some microinverter and optimiser manufacturers offer longer warranties than a string inverter's. On paper, that is an advantage. In practice, the part may be covered while the labour of going up to change it is not. And a decades-long warranty is worth only as much as the manufacturer who signs it: ask for it in writing, with make and model, as we do in every quote.
A fault is not a question of if, but of when. In a well-built installation, the panels last longest and the electronics are what gets replaced first. The difference between the options is not avoiding the fault: it is where it catches you and what it costs to put right. What we inspect and how often is covered in our solar panel maintenance service.
On a roof with no shade and a single orientation, the difference in production is small and rarely pays for the extra cost. With shifting shade or several orientations they do produce more, because each panel works at its own pace without holding the others back. That is why the right answer comes from measuring your shading, not from a catalogue.
The whole installation stops until it is replaced. In exchange, the unit is on a wall, within easy reach, and swapping it does not mean climbing onto the roof. Its usual warranty is around 10 years depending on the manufacturer, and it belongs in the long-term sums from day one.
With microinverters, only the affected panel stops and the rest keep producing. With optimisers it depends on the fault and the system. In both cases, replacing the part means getting onto the roof and lifting the panel, with the labour cost that involves even if the part itself is under warranty.
It depends on the manufacturer. Some systems require an optimiser on every panel and others let you fit them only where needed. It is one of the decisions made in the study, with your shading measured hour by hour, not before.
Anyone who always offers you the same option is not choosing for you, they are selling what they have in the warehouse. In our study, your roof's shading is measured hour by hour across the whole year, and the electronics follow from that. Tell us where your house is and we will get started.
How that shading is measured and how much orientation and tilt weigh: solar panel shading and orientation.
A Captia Technology company. Chartered, qualified engineers.