I’ll be taking advantage of the negative cost energy to charge my car. How have you got HA set up to take advantage? Is it automating certain appliances running when the rate is lowest?

Yup! No EV here, sadly, and I live in a flat but I’ve got storage heaters and a big hot water tank. I’ve got an incredibly janky template sensor that works out how many hours of heating I need for each room based on the weather forecast and an automation that activates the heaters for that many hours a day at the cheapest times. It can also turn the heating on when the price drops below a certain threshold, currently 0p.