The system itself
Microinverters, optimisers or a string inverter?
The short answer
A string inverter is one device converting the output of a whole string, simplest and cheapest, and most affected by shade and mismatch. Microinverters put a small inverter under each panel, and optimisers put electronics under each panel feeding a central inverter. Both of the latter handle shade and per-panel monitoring far better, and both put electronics on the roof.
The practical differences
- Shade tolerance: module-level electronics substantially reduce the effect of one shaded panel on the rest.
- Monitoring: per-panel data tells you which module has failed. String-level monitoring tells you the system is down.
- Failure and service: a string inverter is one accessible device to replace, usually on a wall. Microinverters and optimisers are on the roof, so a failure means roof access.
- Warranty length differs sharply between architectures and manufacturers, and inverter warranties are generally shorter than panel warranties.
- Expandability and battery compatibility differ, which matters if you might add storage.
The question to ask
Why this architecture for this roof. A shaded or multi-orientation roof has a real technical reason for module-level electronics. A simple unshaded south-facing roof may not, and a string inverter there is a legitimate and cheaper choice rather than a cut corner. An installer who offers only one architecture regardless of the roof is selling what they stock.
Ask what happens when the inverter fails, because it will within the system's life. Who pays for the part, who pays for the labour, and does the workmanship warranty still run at that point.
Also asked
Do microinverters last as long as panels?
Warranty terms vary by manufacturer and are generally shorter than panel warranties, though the gap has narrowed. What matters more than the headline number is who pays for the labour of a roof-mounted replacement, which is often not covered by the product warranty.
General information about solar and about hiring, not advice about your roof or your tax affairs. Incentives, net metering and contractor licensing are set federally, by state, and by your utility, and all of them change. The authority that publishes the rule is the current answer.