The UK is currently experiencing some prolonged windy weather and my all-renewable energy provider offers dynamic pricing. That means cheap energy and even negative-cost energy. This is where my HA instance shines and saves me a fortune on my power bill. Thanks again to the HA devs for this incredible project.
For the curious, I'm using bottlecapdave's excellent Home Assistant Octopus Energy integration via HACS.
I keep thinking about doing something similar as I have an EV, solar, and batteries and Home Assistant to pull it all together but I just can't seem to make the maths work on sites like Octoprice. No matter how much I tweak things it always comes out more expensive than Intelligent Go.
I do at least have an automation setup to make the most of the 2 hours of free energy tomorrow. Better than nothing!
Maybe evcc is helpful for you. It can control EV charging stations and batteries based on fine granular rules: https://evcc.io/