Most US utilities have had a program to turn off your AC unit temporarily for the last decade or two (since the 1970s energy crisis), first with a signal over mains/utility power, more recently using wifi thermostats like Nest ("rush hour rewards") and Ecobee. Soaking up excess energy with hot water heaters in Australia as well (vs reducing coal generator output).

> Early Beginnings: 1970s to 1990s Demand Response emerged during the energy crises of the 1970s. During this period, the U.S. faced significant energy shortages, prompting utilities and policymakers to explore innovative ways to manage electricity demand and avoid blackouts. Initial DR efforts were rudimentary, focusing on direct load control. Utilities could remotely switch off high-energy appliances like air conditioners during peak demand periods. These early programs were primarily designed to prevent grid failures and reduce the need for constructing new power plants .

> In the 1980s, DR programs began incorporating time-of-use pricing, which incentivized customers to shift their electricity usage to off-peak hours by offering lower rates during these periods. This strategy aimed to flatten demand curves and reduce the strain on the grid during peak hours .

https://www.energytoolbase.com/blog/energy-storage/the-evolu...

https://www.energycodes.gov/sites/default/files/2025-01/Tech...