The Nordpool price today in the region where I live is 0.80 NOK/kWh, that's 0.074 GBP/kWh or 0.056 USD/kWh.
Here in the Netherlands there are also contracts like that, but people that are interested in them tend to put a lot of time and effort in then tracking those prices. I don't see regular consumers as a whole ever being interested in that. For now, the benefits are also small, and I happily pay a few percent extra (net) to not have to bother.
I also feel like it's not a good direction to move it: consumer energy markets are actually quite predictable so taking out long term contracts should stay the norm (consumer contracts and supplier contracts). Using car batteries as storage for solar can be addressed better by making it more attractive to charge at work, where I assume most park their EVs in the day, but right now pay full price despite providing a place to store surplus.
So, many people would be able to postpone charging their cars. Steep variable pricing easily would make them do that.
My Tesla S 70D could supply my house for at least 24 hours if it had V2G.
Meanwhile the EV fleet has risen to 3.5% of the total car fleet.
To thoroughly abuse statistics, theres an inverse correlation between EV ownership and electricity use.
https://publikasjoner.nve.no/rapport/2023/rapport2023_35.pdf