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Within 5 minutes a wave of hot water systems switch on in SA adding 250MW of demand to the grid

We are creatures of habit. Look at the spike caused at 11:32pm as something like 27,000 hot water tanks in South Australia suddenly switch on to use cheaper off-peak electricity. This spike is entirely due to pricing plans. It’s entirely avoidable too, but at least it’s predictable. “Scheduled”.

This peak, allegedly, is only a problem if SA is “islanded” — meaning if it can’t rely on the coal generators in Victoria.

Yesterday people were asking why the South Australian demand was peaking at 1am (and why two hours were strangely missing from that graph). “Hot water” is the answer (at least to the first part).

SA Hot water systems add sudden 250MW of demand at 11:30pm. Graph.

This graph comes from the AEMO report in Feb 2016. What follows is their electro-nitty-gritty:

Based on previous experience, and as demonstrated in a separation event on 1 November 2015, maintaining the SA power system in a secure operating state is challenging if there are large changes to the supply-demand balance during a period of islanding.

There is a risk of automatic under frequency load shedding if SA is being operated as an island during the hot water demand peak, [...]