String, Micro, Optimiser or Hybrid Inverter?

Four ways to turn DC into AC

Every grid-connected solar array needs the same thing: a device that converts the direct current a panel produces into alternating current that is synchronised with the grid. Four architectures do that job. They differ far less in raw efficiency than in where the conversion happens and what stops working when one component fails.

• String inverter — a single wall-mounted box converts the whole array. Panels are wired in series strings, and each string feeds one MPPT (maximum power point tracking) channel.
• Power optimiser — a small DC-DC converter sits behind every panel, conditions that panel's output, and hands clean DC to a central string inverter on the wall.
• Microinverter — a complete inverter sits behind every panel or pair of panels. Conversion happens on the roof and what comes down the cable is already AC.
• Hybrid inverter — a string inverter with a battery port and, in most cases, a backup output that can run part of the house when the grid is down.

InverterData records the architecture in the inverter_type specification on every model page. You can browse the battery-capable units on the hybrid inverters filter page, or work through the whole catalogue from all inverters.

The four topologies side by side

String inverters: the default, and usually the right one

A string inverter is one box doing all the work, which is why it is the cheapest architecture per watt and the easiest to service. The Huawei SUN2000-3-6KTL-L1 is a representative residential unit: 6,000 W nominal AC, 98.4% maximum efficiency and 97.8% European efficiency, 2 MPPT channels over a 90–560 V tracking window, 600 V maximum DC input, 12.0 kg, IP65, single-phase. The Fronius Primo GEN24 3.0 sits a size down at 3,000 W with 97.6% maximum efficiency, 2 MPPT channels, IP66 and a -40 to +60 °C operating range. On three-phase supplies the Solis S5-GR3P reaches 98.7% maximum efficiency with 2 MPPT channels, 2% THD and IP66 at 16.5 kg.

The same architecture scales all the way up. The Huawei SUN2000-50KTL-M3 is a 50,000 W commercial unit with 4 MPPT channels, a 200–1,000 V tracking range, 1,100 V maximum DC input and a 49 kg chassis — the same idea, four times the trackers and four times the weight.

The MPPT channel count is the number that matters most. Two channels means two roof planes can be tracked independently. It does not mean two panels can be tracked independently: inside a string, the weakest panel sets the current for all of them.

Power optimisers: panel-level DC, one AC conversion

Optimisers split the job. Each panel gets a DC-DC converter that runs its own MPPT and feeds a fixed string voltage back to the central inverter, so the inverter itself can be simpler and run at a constant operating point. That is why the SolarEdge units post the highest inverter efficiency figures in the database: the SolarEdge SE6000H records 99.2% maximum efficiency and 97.5% European efficiency at 6,000 W, 11.9 kg, NEMA 4X, with the smaller SE3000H at 3,000 W and 10.5 kg on the same 99.2% figure.

Read that number carefully. It describes the wall unit alone. The optimisers do their own conversion before the DC reaches it, and that stage has its own loss, so the system efficiency is lower than the headline. What you buy with optimisers is not efficiency — it is per-panel tracking and per-panel monitoring.

Microinverters: everything happens on the roof

A microinverter is a complete grid-tied inverter sized for one or two panels. The GoodWe MIS is 800 W nominal and 800 W maximum AC with 96.4% maximum efficiency, 2 MPPT channels and an IP67 enclosure. That IP67 rating is the giveaway: this device is built to spend twenty years under a panel, exposed to everything the roof gets, while the string and hybrid units above are IP65 or IP66 boxes designed for a sheltered wall.

Microinverters give the finest granularity available. Each panel tracks independently and reports independently, so a soiled or shaded module costs you that module's output and nothing else.

Hybrid inverters: a string inverter with a battery port

Electrically, a hybrid is a string inverter with a bidirectional battery stage bolted on. The Deye SUN-3/3.6/5/6K-SG04LP1 delivers 6,000 W nominal and 6,600 W maximum AC, 97.6% maximum and 96.5% European efficiency, 2 MPPT channels over 150–425 V, 500 V maximum DC input, 230 V output, 3% THD, IP65 — at 17 kg against 12.0 kg for the Huawei string unit of comparable output. The extra five kilograms are the battery stage and its magnetics. The SMA Sunny Boy Smart Energy takes the same approach with 3 MPPT channels, 500 V maximum DC input and 230 V single-phase output, and the Solis S6-EH1P is a 2-MPPT single-phase storage unit in the same class.

Note the tracking windows. The Deye hybrid tracks 150–425 V; the Huawei string unit tracks 90–560 V. A narrower window constrains how many panels you can put in a string, so a hybrid is not always a drop-in replacement for the string inverter you already sized.

Off-grid and marine installations are a separate branch again — the Victron Inverter RS Smart Solar is 6,000 W at 230 V with an 80–450 V tracking range and 450 V maximum DC input, in an 11 kg chassis built around a battery rather than around the grid.

Where the failure sits

This is the argument that decides most installations, and it is not about probability — it is about access. A string or hybrid inverter fails as a single point: the array stops producing until someone replaces the box on the wall, which is a ground-level job. A microinverter fails as one panel out of twenty, so production barely moves — but the replacement is on the roof, which means scaffolding or a lift. Optimisers give you both: a wall unit that can take the array down, plus one roof-mounted device per panel.

Ask the question in that order. How bad is one outage, and how expensive is one visit?

Rapid shutdown and module-level electronics

Where regulations require conductors to be de-energised at the module during a fire — the module-level rapid shutdown rules that apply in the United States, and equivalent requirements elsewhere — microinverters and optimisers satisfy it inherently, because there is no high-voltage DC on the roof to shut down in the first place. A plain string or hybrid inverter needs add-on rapid shutdown devices, one per module. Budget for those before comparing the headline price of a string system against a microinverter system.

Which roof, which household

• Simple roof, one or two orientations, no shading, no battery planned. A string inverter with enough MPPT channels for your roof planes. Cheapest, fewest parts, one service point.
• Shading from a chimney, a tree or a neighbouring building, or panels on three or more planes. Optimisers or microinverters, so one bad panel does not set the current for the string.
• Complex or segmented roof where you may add panels later. Microinverters, because each panel is an independent system and expansion does not force a string redesign.
• Battery now, or a firm plan to add one. A hybrid. Retrofitting storage onto a plain string inverter means adding a second box and a second conversion stage.
• High-value backup requirement. A hybrid with a documented backup output, plus the switchgear described in hybrid inverters and battery storage.

If you are still working out the sizing and phase count before you pick an architecture, start with how to choose a solar inverter, then use the comparison tool to put two candidates side by side.