The strange case of 26th June 2023

The data on my UK electricity generation page is automatically updated every day. A couple of months ago I was looking at the latest update and noticed some of the top level records had changed but not on the previous day. It's not unusual for recent data to get updated but now the data was saying a number of electricity generation records had been broken on 26th June 2023, over 2 years ago.

Initially I thought this was an error in the data and it would be corrected at some point but here we are 2 months later and the data remains the same. So what's up? Why was the data updated and why so long after the actual event?

I did some Googling for uk electricity generation 26th June 2023 but nothing turned up. I also did a search on Bing and my page came up as the top result so that's nice but it couldn't tell me anything special about that day. I even tried asking ChatGPT, which proved even less useful. 

So all we can do is look at the data for the day and for the previous day. The 25th was a good day for solar and wind generation and as the sun disappeared, gas started to ramp up as it usually does. But at 6pm, gas generation started to fall fairly dramatically until 10pm. Then it continued to fall but at a much slower rate. This continued until 5:30am on the 26th, when gas reached virtually zero generation. After this, things fairly rapidly returned to normal.

So what happened? Why did gas generation reach a new record low that we've never got close to again? One possibility is that this a data glitch, but why was did it appear in the data set two years after the event? One reason this looks like it could be the correct answer is that it doesn't look like we were actually producing enough power during the evening of the 25th (although it is possible we were importing more than usual).

But a more interesting theory is that this was actually an experiment to see how the grid coped with mostly clean energy sources. It's my undersanding that electricity generation that involves turbines helps keep the grid's AC frequency in sync, so there have been some questions about how we deal with that when most of our electricity comes from renewables. The fact this weirdness happened in the middle of the night and the gradual withdrawal of gas from the mix gives some credence to this theory. And if that is what happened, the fact we haven't come close to these low levels of fossil fuel usage again may suggest the test was not completely successful.

Anyway, I am going to ask NESO what is happening with that day's data and will let you know if I get a response.