Edit: removed first sentence.
Demand for solutions providing power for days simply does not exist currently. Hours is good enough. This business is about providing lots of power quickly.
You are right that they typically are only used for a few minutes to deal with peaks in demand. That's because they are only needed for that long and because you can turn them on and off pretty much instantly. You don't have that choice with traditional solutions like gas plants.
Which is why despite battery cost, this type of battery is very successful at largely removing the need for having peaker plants. It also seems to be very successful at getting rid of blackouts because there were never enough of those peaker plants to begin with in Australia. Another advantage is that you can put these batteries all over the place. Many small installations make up for a lot of aggregate capacity. You can put them in buildings even; and people do.
Musk is also building factories that are producing batteries by the GWH per year per factory and soon TWH per year. He's not alone of course and basically there are quite many other companies now planning their own little GWH production facilities. There are tens of billions being invested in that stuff in the next few years. There will be hundreds or thousands of these factories in a few decades churning out many TWH of storage annually.
That battery capacity is of course mostly intended for the transport sector and not for grid storage. But if you are worried about having enough storage capacity on the grid, there will be multiple TWH of batteries driving around on roads in most countries by the end of the decade. Basically 2M cars with 50KWH batteries == 1TWH. That's a lot of distributed and mobile storage. All we need to do is plug it in.
Of course there will be more optimal solutions as well. But it's capacity we'll have none the less.
Apparently "Total electricity generation in Australia was estimated to be 265,117 gigawatt hours (GWh) in calendar year 2019"[1], which works out to about 30 gigawatts continually for a year.
So a 1.2GWh battery could power Australia for about two minutes (...at average use. Longer in the middle of the night).
Maybe a hundred installations like that could buffer the fluctuations in renewables in Australia. Plus thousands or tens of thousands more worldwide, while building enough batteries to replace all the cars with electric.
I guess it's doable in a decade or two, if Musk and other manufacturers can really produce TWh's of capacity each year.
1: https://www.energy.gov.au/publications/australian-energy-sta...
Those TWH factories are being built right now. Multiple of them. Production ramp up is going to take a few years before they actually produce that much. But you can sort of do the math based on the number of cars they are selling. About half a million last year so that would be roughly a quarter TWH if you assume 50KWH batteries. Ballpark enough to keep Australia running for about a year if your numbers are correct.
That's last year. It's easy to see how they would grow production to a few million units in the next few years. So, at that point they are using TWH of production capacity that they are building right now in Texas, Berlin, Shanghai, and soon possibly India.
Of course the broader industry is growing quite rapidly to probably a few million unit sales this year and tens of millions by the end of the decade. So, definitely already into TWH/year territory right now. Taking care of Australian energy storage needs is not going to be an issue. About a million EVs would do the trick easily. Sadly, they are a bit behind on jumping on that band wagon but they'll catch up soon enough.
It is one battery in, if memory serves, the state of Victoria.
It is not being asked to power all of Australia.
Your comment would be fine without the first sentence.