TL;DR:

  • String inverters are cheapest and most reliable for simple, unshaded south-facing roofs — they convert DC from all panels combined
  • Microinverters (like Enphase IQ8) convert DC to AC at each panel individually, so shade on one panel doesn’t reduce output from the rest
  • DC optimisers (SolarEdge) are a middle ground: panel-level optimisation with a single centralised inverter, usually cheaper than microinverters with similar shade handling

Most solar quotes present one inverter technology without much explanation. The installer has a preferred supplier, and you’re left wondering whether the system on your neighbour’s roof — which uses a different brand — would have been better. Understanding the three main inverter types takes about ten minutes and can meaningfully affect your system’s long-term performance, especially if your roof isn’t ideal.

How Solar Inverters Work (the Brief Version)

Solar panels produce DC electricity. Your home runs on AC. The inverter converts one to the other.

The difference between inverter types is where in your system that conversion happens, and how much intelligence sits at each conversion point.

String Inverters

A string inverter connects all your panels in series (the “string”), receives the combined DC output, and converts it to AC in one central unit. It’s the simplest and cheapest approach, and for a straightforward installation — south-facing roof, no shading from chimneys or trees, all panels at the same tilt — it works very well.

The limitation is the Christmas lights problem. If one bulb on an old string of Christmas lights fails, the whole string goes dark. With a string inverter, if one panel produces less power (because it’s shaded, dirty, or degraded), the whole string’s output drops to match the weakest panel. Modern string inverters have reduced but not eliminated this effect through maximum power point tracking (MPPT), and many higher-end units have two or more MPPT inputs to handle panels on different roof faces.

Typical cost in the UK: £500–£1,200 for a 4–6 kW system inverter (installed). Brands: SMA Sunny Boy, Fronius Primo, GivEnergy, Solis, Growatt. Battery-ready “hybrid” string inverters (which also manage a home battery) are £800–£2,000 and are increasingly the default choice for new installations.

When it makes sense: Unshaded south-facing roof with all panels at the same orientation. Simple installation, proven reliability, easiest to replace if it fails.

Microinverters

A microinverter sits on the back of each individual panel and converts that panel’s DC output to AC immediately. There is no string; each panel operates independently. Shade on one panel has no effect on any other.

The performance benefit in shaded or complex installations is real. If a chimney shades two panels for part of the day, those two panels underperform in isolation while the rest of the array runs at full capacity. With a string inverter, those two shaded panels would pull down the whole string during that period.

Microinverters also simplify expanding your system later. Adding panels means adding microinverters — you don’t need to check compatibility with a central inverter or worry about string sizing.

The main provider in the UK is Enphase, whose IQ8 series is the current standard. The IQ8 has a significant feature most people don’t know about: it can form a grid-independent microgrid using just panels and batteries, providing some power even during a grid outage. This requires compatible batteries and configuration but is a genuine capability that string inverters can’t easily match.

Typical cost in the UK: Add £100–£150 per panel over a string inverter system for a 12-panel system, so roughly £1,200–£1,800 more upfront. The gap narrows on larger systems due to economies of scale.

When it makes sense: Roof with any shading — chimneys, dormers, neighbouring trees. Multiple roof faces or orientations. Future expansion planned. Long-term performance matters more than lowest upfront cost.

DC Power Optimisers with a Central Inverter

DC optimisers (most commonly SolarEdge) are a hybrid approach. Each panel has a small device attached that optimises that panel’s DC output independently, handling the shade isolation problem. But instead of converting to AC at each panel, the optimised DC runs to a central SolarEdge inverter where the conversion happens.

The result: panel-level performance monitoring and shade tolerance at lower cost than a full microinverter system, because you’re still using a single inverter rather than one per panel. The SolarEdge monitoring app is excellent — you can see individual panel output in real time.

The trade-off is that you still have a single inverter as a potential failure point. If the central inverter fails, the whole system stops. With microinverters, other panels keep working even if one microinverter fails.

Typical cost in the UK: Roughly £300–£700 more than a basic string inverter system for a 12-panel installation — less than full microinverters.

When it makes sense: Some shading but not severe. Good middle ground between cost and performance. SolarEdge’s monitoring and warranty support (12-year standard, extendable to 25 years) are strong.

Which One Should You Choose?

Start with your roof’s shading situation. If your roof is unshaded and south-facing: a quality string inverter or SolarEdge optimiser system will perform very similarly, and the string inverter costs less. If there’s meaningful shading at any time of day, microinverters or optimisers will recoup their extra cost in output.

Check whether the quote includes a battery or battery-ready hybrid inverter. A standard string inverter without battery-ready capability will need replacing if you add battery storage later. Most installers now default to hybrid inverters even when no battery is planned immediately, which is sensible.

Ask about monitoring. All modern inverter systems include some level of app-based monitoring; the quality varies. SolarEdge and Enphase both have excellent monitoring platforms. Some budget string inverter brands have basic monitoring that doesn’t show individual panel performance.

Finally, ask about warranty. Enphase microinverters carry a 25-year warranty as standard. SolarEdge optimisers are 25 years. String inverters typically warranty for 5–12 years with extended options. Since the inverter converts current continuously for 20–25 years, warranty terms matter.

For most UK semi-detached or detached homes with any roof complexity, the SolarEdge optimiser route offers the best balance of shade handling, monitoring, cost, and warranty. For simple unshaded roofs, a quality hybrid string inverter with battery-ready capability is perfectly sufficient and simpler to maintain.