String inverters vs microinverters: which should you recommend? An installer-focused comparison covering cost, performance, shading, monitoring, and when to use each.
Felix Rusby
Choosing between string inverters and microinverters is one of the most common design decisions in residential solar. The right choice depends on the property, the customer's priorities, and the installer's operational preferences.
For most UK residential installations on unshaded roofs, a string inverter with power optimisers offers the best balance of cost, performance, and serviceability. Microinverters are the better choice for complex roof layouts, significant shading, or customers who want panel-level monitoring. Neither is universally "better". The right answer depends on the specific installation.
A string inverter is a single centralised unit, typically wall-mounted near the consumer unit or in a garage, that converts DC electricity from a series-connected "string" of solar panels into AC electricity for the home.
Panels are wired in series to form strings. A typical UK residential system (3-4 kWp) might have a single string of 8-12 panels. Larger systems may use two or more strings connected to a single inverter or a multi-MPPT (Maximum Power Point Tracking) inverter.
SolarEdge, GoodWe, Solis, Fox ESS, and Huawei are among the most commonly used string inverters in the UK market. Many now include hybrid functionality for battery storage integration.
A microinverter is a small inverter attached to each individual panel (or sometimes shared between two panels). DC-to-AC conversion happens at the panel level, and AC power is sent directly down from the roof.
Each panel operates independently with its own microinverter. Panels connect in parallel on an AC bus cable that runs along the roof and down to the consumer unit. This means each panel's output is independent of every other panel.
Enphase dominates the microinverter market globally. AP Systems (APsystems) and Hoymiles are also gaining market share, particularly in the UK and European markets.
Power optimisers sit between string inverters and microinverters. They are DC-DC converters attached to each panel that optimise output before sending it to a centralised string inverter.
SolarEdge is the most well-known example. Their system pairs panel-level optimisers with a dedicated string inverter.
| Factor | String inverter | String + optimisers | Microinverters |
|---|---|---|---|
| Unshaded, simple roof | Best choice | Overkill | Overkill |
| Partial shading | Poor choice | Good choice | Best choice |
| Multiple roof faces | Limited | Good choice | Best choice |
| Budget-conscious customer | Best choice | Mid-range | Most expensive |
| Customer wants panel monitoring | Not available | Available | Available |
| Large system (10+ panels) | Good choice | Good choice | Cost adds up |
| Small/complex system | May not fit | Good choice | Best choice |
| Battery storage planned | Hybrid inverter (simple) | Hybrid inverter (simple) | AC coupling needed |
| Future expansion likely | Requires planning | Easier | Easiest |
Exact pricing varies by manufacturer and supplier, but here is a general guide for a typical 4 kWp (10-panel) residential system:
| Component | Approximate cost |
|---|---|
| String inverter only | £500 - £1,000 |
| String inverter + optimisers | £1,200 - £1,800 |
| Microinverters (10 units) | £1,500 - £2,500 |
The cost difference narrows on smaller systems and widens on larger ones. Labour time also differs: microinverter installs typically take 30-60 minutes longer due to per-panel mounting.
For installers, the key question is not just hardware cost but total project margin. Microinverter systems can command a premium from customers who value monitoring and shade tolerance, potentially improving margin despite higher component costs.
String inverter failures take the whole system offline, which means an urgent callback. Microinverter failures affect a single panel, which customers may not notice for weeks, meaning less urgent but potentially harder to identify without monitoring.
For installation businesses managing a growing portfolio of systems, the warranty and callback profile should factor into the recommendation. Fewer callbacks means lower servicing costs and better customer satisfaction.
The best inverter choice is the one that matches the specific installation. Rather than defaulting to one technology for every job, consider building a standard assessment into your site survey:
Whichever technology you recommend, being able to clearly explain the trade-offs builds trust with customers and reduces post-installation queries.
The inverter decision is just one part of a well-managed installation process. From initial design through to DNO applications and commissioning, having a system that tracks every job end-to-end helps you deliver consistently, regardless of the technology you install. Payaca does that for solar install businesses, and the survey data your team captures on site feeds straight into the quote.
If you are still deciding how to run that process, we compared the software solar installers actually use and why so many leave a generic CRM behind.
Related reading: Best types of solar panels | Software for solar installers | Book a demo
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