Your solar system won't run the whole house in an outage because the inverter only energises the circuits that were moved onto a backup sub-board during installation, and everything outside that sub-board stays dead until the grid returns — no matter how hard the panels are working at the time. The panels and battery decide how long those backed-up circuits can run. The circuit split decides what runs at all, and that split is made by an electrician with a screwdriver long before the first outage.
Come and stand in my kitchen with me.
It's 20:12 on a Tuesday, stage 4, and I'm doing what I always do at that moment: listening. Not to the radio. To the house.
There's a click from the passage — the inverter's transfer relay, one dry snap — and then the second sound arrives a beat later, which is the geyser element letting go. A low hum you never notice while it's running. Then the fridge compressor shudders, the microwave clock blanks, and the telly flickers once before the picture comes back.
The passage light stays on. The router stays on. A minute later the fridge starts up again, because the fridge is on the backup side.
That's the whole story in about eight seconds, and it almost never gets explained properly because everyone is too busy arguing about kilowatts.
What the inverter is actually doing while you stand there
In those first two seconds, my inverter is not deciding how to help. It's checking whether the grid is genuinely gone, and then it's getting out of the way.
A grid-tied inverter without a battery is a current source. It doesn't create voltage — it follows the grid's voltage and frequency and pushes current into it. When the grid collapses, there's nothing left to follow. The inverter has no reference, and more importantly it must not become one. If it kept energising the cable outside my yard while a municipal worker was up a pole on the same feeder, that's not an inconvenience, that's a death. So it stops. Within a fraction of a second it disconnects, and the anti-islanding protection does exactly what it was designed to do.
The bitter version of this: it's midday, the panels are at full tilt, the neighbour's borehole is running off your production, and your house is dark. The sun isn't the problem. The missing reference is.
A hybrid inverter is a different animal. It can form its own reference — generate 230 V at 50 Hz from the battery — and hold that up for the circuits connected to its backup output. That's the click I hear. The inverter has taken over as the source, and the transfer from grid to internal supply happens inside it. Some installs use an external changeover instead, manual or automatic, but the principle is the same: one source is opened, another is closed, and the house is deliberately split into two.
The split is the decision nobody discusses at quote stage
When I was getting quotes, every conversation started with panels and kilowatt-hours. Nobody asked which plugs.
Then the electrician arrives with a clipboard and walks the house. Geyser? Off the backup. Stove and oven? Off. Pool pump? Off. Aircon? Off. Lights, plugs, fridge, router, telly, garage door, the plug by the kettle? On.
That's it. That's the moment load shedding gets decided, and it happened months before load shedding.
The reasoning is blunt once you see it. A geyser element is 3 or 4 kW on its own, which is more than most backup inverters want to pass through for an hour, and it would flatten a normal home battery before the geyser had even finished heating. So the backup sub-board is small on purpose. The electrician isn't being stingy; he's protecting the system from a load it was never sized for.
Whole-house backup does exist. I've stood in a house where every circuit stayed live through stage 6, and it was impressive. It was also a much bigger inverter and a much bigger battery, and the owner had made peace with the price. That's a money decision, not a technical miracle.
Two hybrids, same outage, different behaviour
Here's something that catches people: two hybrid inverters of the same rating can behave completely differently at 20:13.
Some will take whatever the panels are making and blend it with battery power, so a 2 kW load in good sunshine barely dents the battery. Others drop to battery only and keep the panels idle until the grid returns. Same outage, same house, opposite result. It comes down to topology and settings, not to the brochure.
So when you're sitting across from a installer, ask a plain question: during a grid outage, does the PV keep serving the backup loads, or does it shut down until the grid comes back? Listen to whether you get a sentence or a shrug. The shrug is also an answer.
02:40, and the battery has had enough
In a long outage, the arithmetic eventually catches up. The battery drops to its cutoff, the inverter beeps, a fault light comes on, and the backup output drops. Now the house is properly dark. Not partially dark. Dark.
What happens next depends on the machine and the settings. On some systems it simply waits for the grid, full stop. On others, when the sun comes up and the battery is allowed to recharge from PV while the grid is still down, the backup output restarts and the house wakes up before Eskom or the municipality does. I've had both. The second one is the reason I check this before I recommend anything to anyone.
That's worth writing into your own notes, because it's the difference between a system that carries you through a two-hour outage and one that carries you through a two-day one.
Where the paperwork ties back to the click
All of this is the reason your municipal SSEG application asks for an inverter with NRS 097-2-1 certification. That standard covers the anti-islanding behaviour I described — the disconnection, the detection, the refusal to energise a dead grid. The Certificate of Compliance from your registered electrician covers the installation side, including SANS 10142-1 obligations. Neither document is admin for its own sake. Both exist because someone once got hurt.
If a quote arrives without a clear story about the inverter's grid-safety certification, that's not a detail to sort out later. It's the thing that decides whether your installation gets approved at all.
What I'd want written down before I signed
Nothing below needs a diagram. It needs to be in writing, in the quote or the handover pack:
- Exactly which circuits are on the backup sub-board, room by room.
- Whether PV continues to serve backup loads during an outage, or the system runs battery-only.
- What the inverter does at low battery, and whether it restarts on solar alone with the grid still down.
- Who submits the SSEG application and who signs off the CoC.
Four lines. That's the difference between knowing what your system will do at 20:12 on a Tuesday and finding out in the dark.
The click is the same click in every house. What it leaves on is different.
