If you have read anything about plug-in solar you have probably come across the term anti-islanding protection. It sounds technical, but the concept is simple and the reason it matters is straightforward. It is also the reason your plug-in solar system shuts off automatically during a power cut.
What islanding means
When the main electricity grid goes down — during a power cut caused by a fault, storm damage or planned maintenance — the local network becomes de-energised. Engineers go out to locate the fault and work on the cables.
Islanding describes a situation where a section of the grid continues to have electricity flowing through it from local generators, even though the main grid has disconnected. If your solar panels are still generating and feeding electricity into the wiring while engineers believe those cables are dead, the engineers are in danger.
This is not a theoretical risk. It is a well-documented hazard that solar generation creates without proper safeguards, and it is why anti-islanding protection is a legal requirement for any grid-connected solar system in the UK, including plug-in systems.
How anti-islanding protection works
The microinverter in your plug-in solar kit continuously monitors the grid supply. It checks the voltage and frequency of the mains electricity and keeps its own output synchronised with it. When the mains power fails — even for a fraction of a second — the monitoring system detects the loss of grid reference and triggers an automatic shutdown. The inverter stops producing electricity within milliseconds and does not restart until stable grid power is restored.
This happens completely automatically, without any action from you. There is no switch to flip, no notification sent to you. The system simply stops and then restarts when the grid comes back.
Why this means no power in a blackout
Anti-islanding is why a standard plug-in solar system cannot power your home during a power cut, even when the sun is shining brightly. The inverter detects the loss of grid power and shuts itself down. Your panels sit there generating DC electricity from the sun, but the microinverter that converts it to usable AC will not operate without grid reference.
This is the fundamental limitation of any grid-tied solar system, rooftop or plug-in. It is not a flaw — it is a deliberate and necessary safety feature. For backup power during outages, a battery-integrated system with an off-grid mode is required. Our power cut guide explains what the options are.
What to check when buying a microinverter
Anti-islanding protection should be present in any CE or UKCA-marked microinverter sold for grid-connected use in the UK. If a product’s documentation does not mention anti-islanding protection, do not buy it for connection to your home’s mains supply. All the major brands — EcoFlow, Hoymiles, Anker SOLIX — include certified anti-islanding protection as standard. It is one of the core requirements of the UK wiring regulations for plug-in solar.