A new data centre near the Bundey substation, north-east of Adelaide, has been reported as needing four substations, two 330kV transmission lines, and "lots of diesel backup." The numbers behind that headline check out, and the diesel side of it is bigger than most coverage lets on.

The numbers: the site draws up to 800MW at full build, with roughly 550MW going to IT load. That's genuinely four substations (three primary plus one bulk supply point) and two grid-scale transmission lines. On the diesel side: the site is built for up to 96 hours of backup runtime, with 500 kilolitres of diesel stored on site and additional day-tanks at each generator, scaling to as much as 1.1 million litres of diesel fuel capacity across the facility. For context, that's roughly the storage capacity of a small regional fuel depot, not a backup generator shed.

Where the framing slips: the operator describes diesel backup as "rarely used", which may well be true in terms of hours run per year. But batteries on site are explicitly sized only to bridge the short gap until the diesel generators start, not to serve as a genuine alternative. The diesel isn't an emergency afterthought bolted onto a clean-energy facility, it's core infrastructure, engineered in from day one, sized at small-refinery scale.

The bottom line: "rarely used" is a true statement about running hours. It's a misleading one about scale and importance. A facility that keeps over a million litres of diesel on hand isn't treating fossil backup as a footnote, it's treating it as the thing that has to work, every single time the grid can't.