From https://en.wikipedia.org/wiki/Hornsdale_Wind_Farm the battery can do 70MW for ten minutes and 30MW for three hours. They also say "capable of discharge at 100 megawatts" but that might be margin of safety.

I wonder if things are limited by cooling? Maybe the battery only has enough cooling to sustain 30MW of output and doing 70MW for ten minutes is all heat soak.

Yep, I am just taking the headline 100MW figure as the output.

I don't know what Australian electricity needs are, but we averaged 500 W over the last year in our 2-person household. This battery would be good for 10000 similar households for a day or 200000 households "for an hour and 20 minutes...ish".

I used UK per capita electrical energy per annum, translated to an average power usage = 0.8KW. 100/0.8 = 120 ish peoples' power use. So yep - off by a mere *1000!

Is that due to airco or electric heating? We have an average of 130W.

The worlds biggest battery is a lot smaller than imagined. I was expecting something the size of a data center