Technology
Microinverters
One inverter per panel mounted on the roof: what per-panel conversion buys, and what it costs.
What a microinverter is
A small inverter fixed to the mounting rail beneath a panel, converting that panel’s DC output to AC on the spot. Instead of one central box handling the whole array, the array becomes a set of independent AC generators connected along a trunk cable.
Some units serve two or four panels rather than one; the principle is the same. The defining characteristic is that conversion happens on the roof and the cable running down into the house carries AC.
How per-panel tracking works
Each unit runs its own Maximum Power Point Tracker. That tracker continuously adjusts the voltage at which it draws from its panel, hunting for the point where voltage multiplied by current is greatest, and re-checking as conditions change.
The consequence is independence. On a string inverter, everything wired to one tracker sits at one operating voltage, so a panel in shade — or simply a panel at a different angle — is forced away from its own optimum and drags the string with it. With one tracker per panel, each module runs at its own peak regardless of what its neighbours are doing.
That independence is the entire value proposition, and it is worth paying for exactly to the extent that your panels behave differently from each other.
Where it is the right choice
Complex shading. A chimney, a dormer, a mature tree, a neighbouring building — anything casting a moving shadow across part of the array for a meaningful part of the day.
Fragmented arrays. Several small groups of panels on different slopes at different angles, where the tracker count on a string inverter cannot cover them and string voltage limits make the layout awkward.
Awkward panel counts. Strings need to fall within a voltage window, which constrains how many panels can go in each. Microinverters have no such constraint, so a roof that takes eleven panels can have eleven.
No DC on the roof. A design preference some owners hold strongly, and occasionally a requirement raised by an insurer.
Where it is not
An unshaded roof with one or two orientations. There, a string inverter produces close to the same annual figure for considerably less money, with fewer components on the roof and simpler servicing. We will tell you when that is your situation rather than quoting the more expensive architecture by default.
Height and access change the calculation too. On a two-storey house with difficult access, the eventual cost of replacing a failed roof-level unit is not trivial, and that belongs in the decision.
Installation implications
Each unit mounts to the rail before its panel goes down, and every connection is a joint that must be made properly and left weather-secure. There are far more of them than in a string system, and the standard of the connector work is what determines whether the array is still trouble-free in ten years.
The AC side needs its own protection and isolation arrangement, and the array circuit is treated differently from a string DC circuit. Labelling matters more, not less, because the next electrician on site needs to know that the roof cabling is live AC.
Monitoring, warranty and cost
Panel-level monitoring comes as standard, and it is genuinely useful — a single underperforming module shows up as a line on a chart rather than as an unexplained shortfall.
Manufacturers commonly warrant microinverters for longer than string inverters. Read the terms rather than the headline: what is covered, whether labour and access are included, and what is required to keep the warranty valid.
On cost, expect a clear premium per watt over a string inverter, plus the cost of a separate battery inverter if storage is planned. On the right roof that premium is recovered in generation and in monitoring value. On the wrong roof it is not, and we would rather say so at quotation stage.
Specification considerations
These are the figures worth comparing when you are reading a quotation. The exact values for the products specified for your installation come from the manufacturer's current datasheet and are stated in your written quotation.
| What to look at | Why it matters |
|---|---|
| Topology | One small inverter per panel or per pair of panels, mounted on the roof beneath the array |
| Conversion point | DC to AC at the panel, so the roof cabling carries AC rather than high-voltage DC |
| Tracking | Independent maximum power point tracking for each panel |
| Wiring | Units connect to a trunk cable running along the array to a junction and then into the consumer unit |
| Battery coupling | AC-coupled only — a separate battery inverter is required for storage |
| Access for service | A failed unit sits under a panel; replacement usually needs roof access and often scaffolding |
| Typical warranty position | Manufacturers generally warrant microinverters for longer than string inverters; terms are product-specific |
Where it works, and where it does not
Strengths
- Each panel tracks its own maximum power point, so a shaded panel does not drag down its neighbours
- No high-voltage DC on the roof, which some owners and some insurers prefer
- Panel-level monitoring shows exactly which module is underperforming without a site visit
- No single point of failure — one unit failing costs one panel's output, not the whole array
- Array layout is not constrained by string voltage limits, so odd panel counts and fragmented roof areas are easy to design
Limitations
- Costs considerably more per watt than a string inverter, and on an unshaded roof buys very little in return
- Puts electronics under the array where replacing a failed unit means roof access and often scaffolding
- Many more components and connections than a single central unit
- Operating environment is harsh — hot in summer, cold in winter, and permanently exposed to weather cycling
- Storage requires AC coupling with a separate battery inverter, which adds a conversion loss and another unit
This page covers one component. For how the whole thing fits together, see solar panels and battery storage.
Common questions
Are microinverters better than a string inverter?
On a shaded or fragmented roof, generally yes. On an unshaded roof of one or two orientations, no — they cost substantially more and generate about the same. The honest position is that microinverters solve a specific set of problems very well, and if you do not have those problems you are paying for a solution you do not need.
What happens when one fails?
You lose that panel's output and the monitoring tells you which one. The rest of the array carries on. The awkward part is the repair: the unit is under a panel on the roof, so replacement means access equipment. That is why we weigh the roof height and access difficulty when advising on architecture, not just the shading.
Can I add a battery to a microinverter system?
Yes, by AC coupling a separate battery inverter. It works, and it is the standard approach. It involves converting AC back to DC to charge, which loses a few per cent compared with a DC-coupled hybrid, and it means a second unit with its own warranty and its own app unless the products are from a compatible family.
Do microinverters last longer than a string inverter?
Manufacturers generally publish longer warranty terms for microinverters, partly because each unit handles a small load. Against that, they sit in a far harsher environment than a unit in a garage. We would not present either architecture as maintenance-free; the specific warranty length and its conditions are on the product datasheet supplied with your quotation.
Related services
- Solar panel installationSurvey, design, roof works, electrical works and commissioning for a domestic solar PV system.
- System monitoring and optimisationGetting proper data out of a system, then changing its settings so it earns more from the same hardware.
- Inverter replacementReplacing a failed or ageing inverter, matched to the array that is already on the roof.
- Solar health checkA one-off independent assessment of an existing system, with a written report on its condition and performance.
The technology behind it
- InvertersWhat the inverter does, how MPPT works, and how the four architectures compare honestly against each other.
- String invertersThe conventional central inverter: how strings are designed, where it is the best value, and where it is the wrong choice.
- Power optimisersPer-panel DC electronics that keep conversion in one accessible box: the middle option between string and micro.
- Monitoring systemsWhat generation, consumption and battery data actually tells you, and what a system needs fitted to produce it.
Property and roof guides
- North-facing and shaded roofsSometimes the answer is no. Where it is not, per-panel electronics, a different roof, an outbuilding or a ground mount.
- East-west roofsLess annual total than south, a flatter daily curve, higher self-consumption — and a design that pairs naturally with storage.
- Victorian terracesNarrow slate slopes, party walls, rear back-additions and scaffolding through a shared alley — terraced solar on its own terms.
- Listed buildings and conservation areasWhere permitted development rights are reduced or removed, listed building consent is a separate process, and design choices decide the outcome.
Further reading
- String inverter vs microinvertersHow central and module-level conversion differ in shading tolerance, servicing, monitoring and failure behaviour.
- Roof orientation and shadingHow aspect, pitch and obstructions change what a roof can produce, and what can be done about shading.
- Signs your solar system is underperformingHow to tell a genuine fault from normal seasonal variation, and the checks worth doing before calling anyone out.
Where we work
Information reviewed on 2026-08-23.
Not sure which specification suits your roof?
We design around the property rather than fitting the same system to every house. Tell us the postcode and we will explain what we would specify and why.
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