Microinverter
A small inverter mounted behind one or a few PV modules that converts their DC output to AC at module level, with individual power point tracking.
Microinverters perform DC-to-AC conversion at each module, so the array is wired as parallel AC branches rather than high-voltage DC strings. Each unit has its own MPPT, so a shaded, soiled or differently oriented module affects only its own output. Enphase popularised the architecture in the late 2000s; units today are rated about 250–500 VA per module, with dual- and quad-module variants.
Advantages:
- No string-level mismatch; useful on complex roofs with several orientations or partial shading.
- Low DC voltage (below about 60–80 V), simplifying rapid-shutdown compliance under the US National Electrical Code (NEC 690.12) and lowering DC arc-fault risk.
- Module-level monitoring and easy expansion one panel at a time.
- Long warranties, often 25 years, versus 10–12 for string inverters.
Drawbacks:
- Higher cost per watt, typically 0.15–0.30 USD/W more than a string inverter system at residential scale.
- Weighted efficiency of about 96.5–97.5% (CEC), slightly below large string units.
- Many electronic units exposed to high temperatures on the roof; replacement requires roof access.
Microinverters dominate residential PV in the US and are standard in plug-in balcony systems in Germany, where units up to 800 VA can be connected to a household socket under 2024 rules. For large, unshaded arrays, string inverters remain cheaper.
Related terms
All terms →- String inverter
An inverter that converts the DC output of one or more series strings of PV modules into grid-synchronised AC, typically with several independent MPPT inputs.
- Power optimizer
A module-level DC-DC converter that tracks each panel maximum power point and conditions its output before it enters a string inverter.
- MPPT (Maximum Power Point Tracking)
Control algorithm in an inverter or charge controller that continuously adjusts operating voltage so a PV array delivers its maximum available power.
- String (PV)
A group of PV modules wired in series so that their voltages add up while the current stays that of a single module.
- Bypass diode
A diode wired in parallel with a group of cells in a PV module that lets string current flow around shaded or faulty cells, preventing hot spots.