String vs central inverter (residential vs commercial)

"String" and "central" inverters both convert DC to AC, but they live at opposite ends of the scale spectrum. The right choice is driven almost entirely by system size — which is why homes and solar farms look so different. Here is how the two compare and where each belongs.

The core difference is scale

• String inverter — a compact unit that converts DC from one to a few series strings of modules, typically a few kilowatts up to tens of kilowatts. Used in residential and small commercial systems.
• Central inverter — a large, cabinet-sized unit that converts DC from many combined strings, rated from hundreds of kilowatts to multiple megawatts. Used in large commercial and utility-scale arrays.

The names describe the architecture: strings feed a modestly sized inverter, while a central inverter centralizes conversion for an entire large array through combiner boxes.

How the wiring differs

• In a string system, module strings connect directly (or through a small combiner) to the string inverter, then to the service. Wiring is straightforward and sized for residential loads.
• In a central system, strings land in combiner boxes in the field, which aggregate them into large DC feeders running to the central inverter. This requires switchgear, DC collection, and often a dedicated equipment pad.

Redundancy and maintenance trade-off

Scale changes the failure math:

• With string inverters, a single unit failing takes down only its portion of the array, and units are relatively easy and cheap to swap. Larger sites simply use more of them.
• With a central inverter, one failure can idle a large block of the array until service — but there are far fewer units to maintain, and cost per watt is lower at scale.

For a homeowner, this is why residential design never reaches for a central inverter: the scale does not justify the infrastructure, and string inverters (or microinverters) offer better granularity and simpler service.

Where each fits

• Residential — string inverters or microinverters. For the module-level options, see microinverters vs string vs optimizers and what is a microinverter.
• Small commercial — string inverters, sometimes many in parallel.
• Large commercial / utility — central inverters with field combiners, or increasingly "string inverters at scale" (many large three-phase string units) as an alternative to a single central unit.

That last trend blurs the line: some big projects now deploy dozens of large string inverters instead of one central unit, trading some cost for redundancy.

For homes, the practical choice is always a string inverter or microinverters — central inverters belong to utility-scale projects. Confirm inverter specs against the datasheet, and have a licensed electrician or PE review the design. New to sizing? Start with how to size a residential solar system or try the DIY workflow.

Educational reference, reviewed 2026-07. A design aid, not a substitute for a licensed electrician or PE. Confirm the enforced NEC edition and local amendments with your AHJ.