This is where i got the number from @brydo.
And they also say, but obviously this won’t apply to me since i don’t use their Hive Smart Charge.
https://www.britishgas.co.uk/energy/gas-and-electricity/ev-tariff.html
With SmartCharge, you could get a 4p/kWh credit saving on all your EV charging with Hive SmartCharge.2 Combine this with our Electric Driver tariff, and you could be paying an equivalent of just 3.9p/kWh if you plug in overnight between 12am – 5am.