Some domestic users can (for things like AC, heaters etc)
For industrial, they can establish peak-times and broadcast the pricing info. So maybe not "seconds" but they can react to demands and pricing. It is possible (and depending on the industry, likely) that some industries do have backup power on site, so they switch to that and stop using grid power.
I don't think raverbashing was talking about the state turning it off, but rather individual people turning their own AC/heating off.
Nest Thermostat offers many features to automatically do this if users want it, both to save money, as well as to help the planet. Full disclosure, I work at Google, but not Nest.
> "I think it's clear that one of the issues facing aluminum is that it is costly to bring down smelting capacity and even more costly to bring it back up again," Harvey said during a virtual presentation at the Bank of America Securities Global Metals, Mining & Steel Conference. "I think it has tended to be a relatively slow process for producers to come to those decisions."
> Harvey said each potline at a smelter requires about $25 million to restart, which made it challenging for operators to reach curtailment decisions.
In the long term, I expect this to become very common as hydrogen replaces methane in ammonia production and coal in steel production. Hydrolysis can happen when price is low and as long as the hydrogen buffer is big enough it will last through high prices.
Eg: google/facebook datacenters, aluminum smelters, factories, etc.