Most energy providers advise shifting circa 40% of peak rate electricity to those cheaper hours. This is because the day rate pence per kWh is inflated above the standard variable rate in most cases, which essentially loses access to cheap electricity fixes. However, you don’t have to, and in most circumstances you’ll still be better off than running an ICE.
I’m with Octopus Go with my PHEV—my last bill saw me using 152.6 kWh (£12.35). At the peak rate, I used 149.7 kWh (£41.63) ex vat. So when you offset how much petrol it would have cost to cover 400 miles a month compared to how much it cost in electricity taking my daughter to and from school, I have still saved a small fortune even though I haven’t shifted any daytime electricity to the cheap off-peak hours! As an electrician, I don’t advise running white goods, etc., overnight whilst asleep; neither does the fire brigade.
Intelligent tariffs are slightly different, but the same basis applies.