AI illustration: Australia's big battery in 100 days or it's free
TeslaCars & Energy
Delivered

Australia's big battery in 100 days or it's free

“Tesla will get the system installed and working 100 days from contract signature or it is free. That serious enough for you?”
— Elon Musk · Mar 10, 2017 · Elon Musk on Twitter, March 10 2017, replying to Atlassian's Mike Cannon-Brookes (verified via publish.x.com oEmbed) ↗
See his original post on XLoads Elon's actual tweet, right here.
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What actually happened

Tesla delivered. The 100 MW / 129 MWh Hornsdale Power Reserve in South Australia — then the world's largest lithium-ion battery — was built in roughly 60 days from the grid-connection agreement and officially switched on December 1, 2017, comfortably inside the 100-day bet window. One of Musk's cleanest wins. BBC — Tesla mega-battery in Australia activated ↗

The Progression

Mar 10, 2017
The promise: “Tesla will get the system installed and working 100 days from contract signature or it is free. That serious enough for you?” · Elon Musk on Twitter, March 10 2017, replying to Atlassian's Mike Cannon-Brookes (verified via publish.x.com oEmbed) ↗
Dec 1, 2017
Delivered — on time. Tesla delivered. The 100 MW / 129 MWh Hornsdale Power Reserve in South Australia — then the world's largest lithium-ion battery — was built in roughly 60 days from the grid-connection agreement and officially switched on December 1, 2017, comfortably inside the 100-day bet window. One of Musk's cleanest wins. BBC — Tesla mega-battery in Australia activated ↗
Today · Jul 16, 2026
Status: Delivered · on time. It happened.

The famous '100 days or it is free' Twitter bet of March 2017 with Atlassian co-founder Mike Cannon-Brookes committed Tesla to building a 100 MW grid battery for blackout-plagued South Australia. The Hornsdale Power Reserve went live December 1, 2017, within the window, and went on to slash grid-stabilization costs — a rare unambiguous early delivery among Musk's public promises.

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