Compare conversion, tracking and shared equipment—not a winner by topology.
Topology concept only. One string is shown; an inverter may have several strings and MPPT inputs. Not a wiring diagram.
POINT 1
Group the right modules
A string connects modules to a shared inverter input. Track the actual strings and MPPT allocation; a multi-MPPT inverter does not place the whole array at one operating point.
POINT 2
Conversion at the inverter
A string inverter converts DC to AC. Its exact voltage, current and tracker limits decide whether the proposed groups are suitable.
POINT 3
Conversion at each module
Microinverters provide module-level conversion and tracking. The benefit for a particular roof still depends on the products, layout and operating conditions.
POINT 4
Independent is not isolated
AC branches, protection, gateways and the site connection can remain shared failure points. Record both the device boundary and the shared boundary.
A string inverter can have one or more MPPT inputs; only modules assigned to the same electrical string and tracker should be treated as one group.
Microinverters give modules independent conversion and tracking, but branch circuits, communications and grid equipment can still be shared failure points.
Do not infer shade gain, warranty life, cost or expandability from topology. Compare the exact models, layout, portal access, warranty terms and approved design.
Both topologies convert PV output from DC to AC. A string inverter serves one or more strings and may provide several MPPT inputs. A microinverter sits at module level and controls that module's operating point. See AC vs DC solar panels for the full energy path.
Compare the actual design
String and MPPT allocation: identify every module on each string and tracker. Do not describe a multi-MPPT inverter as controlling the whole array at one operating point.
Shade: trace when and where shade lands. Bypass paths, module layout and inverter controls affect the loss; a topology label cannot provide a reliable percentage.
Electrical limits: verify cold open-circuit voltage, operating voltage, current, power and permitted string lengths using the exact documents.
Monitoring: confirm whether module-, string- or system-level data is available to the installer and owner, and whether access depends on a gateway, account or subscription.
Service boundary: record what stops when a device, branch, gateway or shared inverter fails, and what roof access a replacement requires.
Field decision
Module-level conversion may suit a layout with different operating conditions or a requirement for module-level visibility. A string inverter may suit a design that can be grouped cleanly across its available MPPT inputs and where accessible central service is valuable. Neither statement is a rule: product limits, network settings, rooftop conditions and the service model can change the result.
Before accepting either proposal
Match the model numbers on the quote, datasheets and design.
Mark roof faces, shade windows, strings, MPPTs and AC branches.
Check operating limits and the intended export-control arrangement.
Read the exact product and performance warranties, including labour, access and transport terms.
Confirm how commissioning data and later diagnostics will be accessed.
For an Australian SRES installation, confirm the exact models are on the approved product lists and installed before the relevant listing expiry.
Use the topology to ask better questions. Use the documented site design to make the decision.
How much more will microinverters produce in shade?
There is no universal percentage. The result depends on shade shape and timing, module bypass design, string allocation, MPPT behaviour and the exact products. Model the proposed layout or compare representative site data.
Which topology suits several roof faces?
Either may work. Check whether each differently performing group can be placed on a suitable MPPT within the inverter's voltage and current limits. Module-level electronics can simplify some layouts, but the exact design decides suitability.
Does a microinverter system have no single point of failure?
No. One microinverter fault may affect one module, but AC branches, protection, gateways, communications and the site connection can affect more of the system. Document the failure boundary and service access for the proposed equipment.