Solar inverters explained: string, micro and hybrid

A solar inverter converts the direct current your panels produce into the alternating current your home and the grid use. There are four main types: string, string with power optimisers, microinverters, and hybrid. The one you choose shapes your yield, your resilience to shade, and whether you can add a battery without rewiring.

Your panels make direct current. Your home, your appliances and the grid all run on alternating current. The inverter sits between the two and converts one into the other, thousands of times a second. You rarely see it after the installer bolts it to a wall, yet it shapes how much power you actually use, how your system handles a shaded chimney, and whether you can add a battery later without ripping things out.

What the inverter actually does

A solar inverter's job goes beyond simple DC-to-AC conversion. It runs maximum power point tracking (MPPT): sunlight changes by the minute as cloud passes and the angle shifts, so the inverter constantly hunts for the voltage that pulls the most watts from your panels. It also handles grid safety. If the grid drops, the inverter disconnects in milliseconds so it cannot push power onto lines that an engineer might be repairing.

In the UK, your installer registers this under the G98 or G99 connection rules set by the Energy Networks Association. G98 covers smaller systems under 3.68 kW per phase (fit the system, then notify your DNO within 28 days). G99 covers larger systems and requires pre-approval from the DNO before installation begins (Sunsave, 2026; Solar Tech Support, 2026). Other countries run their own equivalents, and your installer files the paperwork either way.

The four types at a glance

String inverters

A string inverter is the long-standing default. You wire panels in series into a "string", and that string feeds one central box, usually mounted in a garage, loft or on an outside wall. One unit handles the whole array, which keeps the price down and gives you a single point to service.

The trade-off is in that series wiring. The string runs at the output of its weakest panel, so one shaded or leaf-covered module drags down every panel on the same string. A modern string inverter with two MPPT inputs softens this by letting you split the roof into two independent groups, a south face and an east face, for example. If your roof faces one direction and nothing shades it, a string inverter is the sensible, economical choice.

Power optimisers

Power optimisers keep the central string inverter but add a small device behind each panel. Each optimiser conditions its own panel's output, so a shaded module no longer holds the rest back. You get per-panel monitoring too, which makes a dead or dirty panel easy to spot in an app. SolarEdge built much of the market here, pairing optimisers with a matched inverter.

You pay more than a plain string setup, and you add one extra electronic component per panel on the roof. For a part-shaded or multi-faced roof, that cost often recovers itself in extra generation.

Microinverters

A microinverter does the full DC-to-AC conversion at each panel. There is no central box. Enphase dominates this approach. Because every panel works independently, shade on one corner costs you only that corner's output, and the system has no single failure point that takes down the whole array. You also get the most detailed monitoring, panel by panel.

Microinverters cost the most per watt, and replacing one means a roof visit. They suit broken, dormer-heavy or multi-pitch roofs where panels face several directions and shade comes and goes through the day. If your roof is awkward, this is where the extra spend goes.

Hybrid inverters

A hybrid inverter does everything a string inverter does and adds a DC connection for a battery. That matters because of how energy moves. With a standard inverter feeding an AC-coupled battery, power converts from DC to AC and then back to DC to charge the battery. You lose a few percent at each step. A hybrid inverter charges the battery on the DC side, skipping conversions and keeping more of what your roof produces.

Buy a hybrid even if you are not buying a battery yet, and you stay "battery-ready". You add storage in a year or two by connecting cells, with no second inverter and no rewiring. Hybrids cost more upfront, and if you are certain you will never store energy, you are paying for a feature you will not use. Most people who care about rising tariffs or evening backup find the headroom worth it. We cover the storage side in detail in solar batteries: when they pay.

Efficiency and what the numbers mean

Inverter datasheets quote peak efficiency and a weighted figure called European efficiency or CEC efficiency, usually one to two percentage points lower because it averages across real operating loads. Treat the weighted number as the honest one.

Modern string inverters reach 97–98% peak efficiency (SMA Sunny Boy: up to ~97.9%, Fronius GEN24 Plus: ~98%); Enphase IQ8 microinverters reach ~97.7% peak (Enphase IQ8 datasheet, 2026). The gap between a 96% and a 98% inverter is real money over twenty years, though it stays smaller than the loss a shaded roof creates, which is the whole argument for optimisers and microinverters.

Inverter sizing: the DC:AC ratio

Installers typically size the inverter so its AC rating is around 77–91% of the DC panel capacity, a DC:AC ratio of roughly 1.1 to 1.3 (Aurora Solar). This works because your panels rarely hit their lab-rated maximum in real conditions: heat, cloud, and angle losses mean actual output runs 75–85% of nameplate for most of the day.

A little "clipping" at peak noon, where the inverter caps output at its AC limit, costs very little in annual yield while letting you buy a smaller, cheaper inverter. At a DC:AC ratio of 1.2, clipping typically loses around 1–2% of annual production (Aforenergy). Your installer will model the right ratio for your roof's orientation and location; ratios above 1.5 start to clip more meaningful amounts and need justification.

Warranties

Here is where the technologies diverge. String and hybrid inverters from leading brands typically carry a 5 to 10 year standard warranty (Fronius and SMA start at 5 years; Sungrow ships with 10 years), extendable to 20 or 25 years at extra cost (Clean Energy Reviews, 2025). Microinverters and optimisers from leading brands come with 25 year cover, Enphase IQ8 carries a 25-year limited warranty designed to match the panel life (Enphase, 2026).

Expect to replace a string inverter at least once across the panels' 25-year life. Factor that replacement cost into your long-term sums, and our payback model does exactly that.

Working out what it means for your roof

The inverter choice changes your yield, your maintenance and your replacement schedule, so it belongs in the economics, not just the spec sheet. We model all of this on free, resale-permitted climate data from PVGIS, NASA and NREL, then show you honest payback, NPV and IRR for your address and your local tariff, in your currency, before anyone asks for your details.

For a full picture of what your system might earn and cost over time, see how to size a solar system and solar payback, NPV and IRR.

Frequently asked questions

What is a solar inverter and why does it matter? A solar inverter converts the direct current your panels produce into alternating current your home can use. It also runs safety disconnects, MPPT to squeeze maximum power from your panels in changing light, and (for hybrid models) manages battery charging. Choosing the right type affects your yield, shade resilience and battery compatibility.

Which inverter type is best for a shaded roof? Microinverters or string inverters with power optimisers. Both give each panel independent operation, so a shaded panel only hurts its own output. A plain string inverter drags the whole string down to the weakest panel's level.

What DC:AC ratio should my installer use? Most residential installs target a DC:AC ratio of 1.1 to 1.3, meaning the panel array is 10–30% larger than the inverter's AC rating. Your panels rarely hit nameplate output in real conditions, so a modest oversize improves yield without meaningful clipping losses.

How long do solar inverters last? String and hybrid inverters typically carry 5–10 year standard warranties and are often replaced once during the 25-year life of a solar panel system. Microinverters and optimisers from leading brands come with 25-year warranties, designed to match the panel life.

Do I need a hybrid inverter if I am not buying a battery yet? It depends on your plans. A hybrid inverter costs more upfront but lets you add a battery later with no rewiring. If there is any chance you will want storage in the next five years (for evening self-consumption, backup power or rising tariff protection), the extra cost is usually worth it.

Estimate your roof →

Estimate only, not a quote. Figures use local climate data and average tariffs; your installer's quote will be exact.