A grid-forming inverter acts as its own voltage and frequency source, so it can run without any other source setting the grid. A grid-following inverter is different: it needs an outside voltage and frequency reference and faults when that reference is lost. In grid-forming mode the inverter still follows real and reactive power commands, but it also tracks voltage and frequency setpoints. It reacts within a fraction of a cycle to hold them at its AC terminals. Because the mode resists sudden changes, it reaches power commands more slowly than grid-following mode. In exchange, it responds much faster to voltage and frequency disturbances. The industry uses two main approaches, machine-based and droop-based. Grid forming can be used off-grid, as backup during an outage, or on-grid to add virtual inertia. In a hybrid system that is grid-forming on PV alone, loads must stay below the available PV power. Otherwise the inverter trips on overload, and repeated trips can require a manual hard reset. Support depends on the product. Enphase supports grid forming only on 240 V IQ8 variants, not on the IQ8 H-208 or IQ8 Commercial systems.
<!-- review notes
related_toc1 drafted · lead Grid-following inverter
Grid-following operation needs an external voltage and frequency source and faults when it is lost. Grid-forming operation acts as a standalone voltage-frequency source. It reaches power commands more slowly but responds much faster to voltage and frequency changes.
sec=2.1.2 h=fc2b174a8b7dsec=2.4.2 h=46138d6d5564c2 verified · fact Grid forming
sec=2.1.2 h=fc2b174a8b7dsec=h1 h=fadcdb955784sec=2.4.2 h=46138d6d5564verified by: review-workflowverified on: 2026-10-24
c3 drafted · lead Inertial response
Scope: products Tesla Megapack platform (generation not stated) proposed
Grid-forming can be enabled while on-grid to add virtual inertia.
sec=2.4.2 h=46138d6d5564c4 drafted · lead Island operation
Grid-forming can be used off-grid (islanded) and for backup when the grid is absent.
sec=2.4.2 h=46138d6d5564sec=h52 h=91e513559c55sec=4.4.3 h=5b712bf9cb1ac5 verified · fact Off-grid system
fig=100 h=dbd1a8796635fig=106 h=1913bff08668sec=4.5.1 h=c7f644ba07e5sec=4.4.3 h=5b712bf9cb1averified by: review-workflowverified on: 2026-10-24
c6 drafted · lead Frequency-Watt
Scope: products Solis S6-EH2P(9.6-16)K-SV-YD-L-US; applications backup, off-grid
When the hybrid inverter is grid-forming, it shifts frequency to curtail AC-coupled PV on its Smart Port once DC PV has been curtailed to zero.
sec=4.4.3 h=5b712bf9cb1ac7 verified · fact AC-coupled storage
Scope: products Solis S6-EH2P(9.6-16)K-SV-YD-L-US
sec=4.4.3 h=5b712bf9cb1averified by: review-workflowverified on: 2026-10-24
c8 drafted · lead Enphase IQ8 Series Microinverters proposed
Only IQ8 variants for 240 V AC interconnection support grid forming; IQ8 H-208 does not.
sec=h1 h=fadcdb955784c9 drafted · lead Tesla Megapack platform (generation not stated) proposed
Grid forming is only available on systems designed for it and must be enabled by Tesla at commissioning.
sec=2.1.2 h=fc2b174a8b7dsec=2.4.2 h=46138d6d5564c10 drafted · lead Black start
Grid-forming systems can operate on grids that have no conventional generation and no other inverter sources.
sec=2.1.2 h=fc2b174a8b7dreview note: support check: partial - u2 supports operation on grids without conventional generation or other inverter sources, but black start is never mentioned.; review: partial - The note about running on grids with no conventional generation and no other inverter sources is stated, but the passage never mentions black start.
related_to c1