Here in UK on certain tariffs (Octopus Agile) price of electricity regularly falls below zero at night. If you have an electric car set to only charge when price of electricity is below zero, you're getting paid to charge your car.
Does Octopus provide the price of electricity at the current moment?
I had a quick look at their website but couldn't see anything obvious.
This website does some analysis on the pricing: https://www.energy-stats.uk/octopus-agile/
The useful part is that, if a user of the tariff is sufficiently engaged, not only do they save money, but by shifting their demand to follow supply it helps with the increasing adoption of renewable sources.
Looks like this:
But if you want, you can also export all of the data as an excel spreadsheet.
Some car chargers(OHME for example) can read this data in real time and only start charging when the price per kWh falls below a pre-set level.