Guide · Architecture
On-grid, off-grid or hybrid?
An ONEE outage hits in the middle of the afternoon. Three houses in the same neighbourhood have panels on the roof; only one keeps the power on. The difference isn't the panel brand or how many there are, it's the architecture chosen. Here's how each of the three behaves when the grid goes down — and why anti-islanding explains most of it.
The on-grid system (grid-connected)
An on-grid system — also called grid-tied — produces solar electricity and consumes it in direct self-consumption, with the ONEE grid acting as a "virtual battery": the surplus goes to the grid, the shortfall is made up by it. It's the most profitable architecture for urban households and businesses connected to ONEE, since there's no physical storage to pay off.
However, during a grid outage, this inverter shuts down immediately — even in full sunshine. That's not a defect: it's a mandatory protection.
Why the inverter cuts out: anti-islanding
The standard requires every grid-connected inverter to have a so-called anti-islanding function: as soon as the grid disappears, the inverter detects the absence of voltage and isolates itself within milliseconds. The reason: if the inverter kept injecting current onto a line that ONEE technicians believe is de-energised, it would pose a deadly risk to intervention crews. The automatic shutdown protects people — not the inverter.
Practical consequence: having solar panels doesn't guarantee having electricity during an outage if the system is purely on-grid.
The off-grid system (autonomous)
An off-grid system isn't connected to the grid at all. It produces, stores in batteries, and returns energy completely autonomously. It's the natural solution for isolated sites — remote farms, telecom relays, unserved rural areas — where there's no grid to join. In an urban setting connected to ONEE, a pure off-grid system is rarely justified economically: sizing storage to cover nights and cloudy days represents a significant investment, without the flexibility the grid provides for free.
The hybrid system: grid + battery + backup
A hybrid system stays connected to the grid for self-consumption and day/night balance, but adds a battery that takes over on priority circuits — lighting, fridge, chargers, internet box — as soon as the grid goes down. A battery of 5 to 10 kWh is generally enough to keep these essential uses running for several hours.
When the outage happens, the hybrid inverter switches to its backup outputs within milliseconds (on the order of 4 to 10 ms on UPS-mode models, up to one or two seconds on others). It isolates these circuits from the grid, which respects anti-islanding, and keeps feeding them. It's the only one of the three architectures that ensures daily self-consumption while keeping the power on during an outage.
Which one for the three houses in the neighbourhood?
Back to the outage from the start. The house connected to ONEE, for which outages remain an occasional nuisance, lives very well with an on-grid system: it's the one that pays for itself fastest. A country house without a power line has no choice, it's off-grid. The third — a medical practice, a shop that can't stop, a remote-work office — pays for its hybrid battery through the continuity it buys. The right benchmark, then, isn't the starting budget but a simple question: what actually happens at your place the day the power stops?