It's practical enough that this is how it works now in many (most?) parts of Europe at least. Electricity at the wholesale level is priced hourly or quarter-hourly and households often elect to have a correspondingly hourly priced eletricity contract & program their appliances/ev charging/whatnot to follow the price.

See eg https://www.euronews.com/business/2025/02/20/fixed-vs-variab...