I'd missed this BBC report from earlier in the week
Emergency text averted possible California power cuts
"An emergency text message helped to prevent possible blackouts in the state of California on Tuesday.
The message asked residents to limit energy use for three hours to cut the risk of power cuts being implemented.
The California Independent System Operator (Cal-ISO), said it "saw an immediate and significant drop" in the use of power after the text was sent.
The alert was issued after record temperatures put pressure on the state's electrical grid."
<Much Snippage>
".....Ms Hill believes that the UK is more resilient to situations like this.
"Ten years ago, UK network operators such as the National Grid and smaller disruption network operators had to assess the climate change risk to all of the systems.
"Due to that assessment, plans were made to manage that risk through damage management, communication or through improving the technology," she said.
A National Grid Electricity System Operator spokesperson told the BBC: "There are established mechanisms in place for communicating in an emergency.
"Due to the nature of these emergency communications and procedures we do not comment on the specifics of how these work."
More at the BBC:
https://www.bbc.co.uk/news/technology-62832775
It's an interesting discussion point though - if you received a text alert here, what would you turn off ? I don't think we're regular users of particularly high power items here at Bobins Towers. There's a lot of low-medium power things, but high power items are rarely used. We've been on LED lighting for years, we have a gas cooker and gas CH. I could probably turn off a few things but it'd amount to 100-200 watts, and the reason they're on now is because they need to be on !