What Happened To Rooftop Solar Yesterday?

Yesterday, 23 May, something strange happened to electricity supplies across the National Energy Market (NEM).

Figure 1 shows total electricity generation for the last three days across Queensland, New South Wales, Victoria, South Australia, and Tasmania.  Notice the huge drop in generation early yesterday afternoon.

Figure 1:  3 Day Generation, NEM

The drop was entirely due to Solar Rooftop generation going from gangbusters at 1:00 pm to zero from 2:00 pm to 3:00 pm.

Figure 2:  All NEM Generation Monday 23rd.

Figures 3, 4, and 5 show the drop in closer detail.

Figure 3:  All NEM Generation 1:00 pm

Figure 4:  All NEM Generation 2:00 pm

Figure 5:  All NEM Generation 3:30 pm

It happened in every state, from Queensland, producing the most solar power (1,376 MW or 18.6% of the Queensland total):

Figure 6:  Queensland Rooftop Solar:

to South Australia, whose paltry 814 MW was 48.4% of total power used.  Interesting that solar in SA fell off from 12:30 pm.

Figure 7:  South Australia Rooftop Solar (12:30 pm):

At 2:00 pm, the drop in energy supply was nearly half (1,659 MW to 849 MW)- and they were still charging batteries.

Figure 8:  South Australia Rooftop Solar (2:00 pm):

By 3:30 pm, SA solar had recovered to 28% of supply- which was also helped by an almost equal amount of imported electricity:

Figure 9:  South Australia Rooftop Solar (3:30 pm):

In case you think this was caused by the cloudy weather over eastern Australia, it wasn’t:  it was mostly clear.

Figure 10:   BOM radar map at 1.30 pm 23rd May

Network generation fell by 16.5% from 1:00 pm to 2:00 pm.  Did no one notice?  Were there no blackouts?  Why was all rooftop solar in eastern Australia closed down for an hour?  Did you know they could do that?  If rooftop solar can be completely shut down without any ill effects why have it in the first place?

I think this will remain a mystery.


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6 Responses to “What Happened To Rooftop Solar Yesterday?”

  1. John Trigge Says:

    In SA (unknown if applies to other states) rooftop solar may be disconnected from the grid for whatever reason the powers-that-be deem necessary. See:


    “Prescribed generating systems connecting to the electricity distribution network in South Australia are required to be capable of being remotely disconnected and reconnected by a Relevant Agent registered with the Technical Regulator.”

    Perhaps there was too much power being generated and depriving the rooftop generators of income, low as this is nowadays, was easiest.

    The dip is not reflected in the solar farm data – https://anero.id/energy/solar-energy/2022/may/23

    • kenskingdom Says:

      Yes, rooftop solar can be disconnected remotely. However there was not too much power being generated- generation on Monday was not unusual when you compare with other days on the NEM graph. Besides, why turn rooftop completely off in every state for a whole hour if generation goes a few percent over?

  2. ptrdxn@bigpond.com Says:

    My humble guess is that authorities conducted EXPERIMENT to PROVE that they could turn off rooftop solar (if they had to in the future), and to monitor what happened. The BLACK line for coal has expanded DOWNWARDS a bit before and during early part of no solar. This CHEATS LINE has partly obscured the replacement of missing solar. Maybe some industries agreed to secret brownout to lessen the instability.

    Good luck with finding alternative scenario. From Peter Dixon at Wodonga.

  3. tonyryan43 Says:

    Probably just testing a global Tesla device to prevent the use of solar power by off-grid resistance fighters after The Final Lockdown. Nothin to worry about. But I have jotted down the need to reintroduce slavery to operate my 100-seat pedal-power generating plant.

  4. siliggy Says:

    Your rain radar piccy does seem to show cloud would have arrived over many populated places around that time. Not so Much S.A. though. A puzzle for sure.

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