Wondering if any Aussies here know this.

I’ve heard that if you have a solar system and a battery system connected to the grid, if the grid goes out for whatever reason, your battery gets cut off as well. Meaning that it’s essentially useless as power backup.

Is this true? Can you really go fully off-grid in Australia?

I’ve heard this from rural people in Victoria, where they do experience blackouts and where an actual backup would be useful.

Many systems, especially older ones, are set up this way by default.

But you can get, for extra $$, a switch to disconnect you from the grid entirely when it's down and run from your own solar power / battery. People who live in cities with underground wires normally don't bother, but it's essential in the countryside (IMHO).

Note however that many people have only maybe 5kW or 8kW or something like that being added to grid power by their solar setup, so if there is no mains power then it doesn't take many 2kW appliances (microwave, kettle, clothes washer (when heating water), dish washer (ditto), hairdryer, vacuum cleaner) to overload it. Not to mention 3kW hot water heater or 3kW+ stove oven.

I have a 3600W off-grid system (Pecron E3600LFP) and I run pretty much all that stuff from it. I added up and I could try to turn on 14kW of stuff at the same time. But I don't, obviously.

It depends on the inverter. Older "grid-following" inverters would isolate themselves from the grid to avoid putting any current on the line when presumably in an outage it should be de-energised, as well as relying on the grid for reference frequency.

Modern hybrid & multi-mode inverters are capable of isolating themselves from the grid, generating their own reference frequency and managing connection and disconnection from the grid. However you might not get one of these types of inverters unless you specifically ask for "backup power" or similar.

I've had solar for ten years and just added a battery to it which _should_ keep the house running through a power failure for as long as the battery holds out.

This is yet to be tested, but it's very specifically setup to me able to.

There are some specific electronics required to continue operation when the grid is down, and with the explosion of popularity of home batteries, I think these options are also more common.

you heard wrong. What most electricity grids forbid is exporting power from your home to the grid when the grid is down. The claimed danger is that energised power lines will kill people working on the lines.

The reality is that the vast majority of home inverters (in an EV, battery or solar PV) is nowhere near powerful enough to energise even a single distribution transformer.

This is yet another example of electricity codes being unrealistically restrictive.

Generally, there's nothing stopping you from disconnecting your home from the grid during a power outage and running your own devices off a battery. Going fully off-grid depends on your local laws.