Sounds overly optimistic as a cost driver.
A third of UK homes don't have off street parking, and a fair chunk of those will be the homes of folk who don't own cars at all. They're living in towns, working locally, and wrinklies sticking to the old tech.
What's the annual saving anyway? Not much more than £500 a year. It's hard to see that driving a change in property values. Asmarter choice of your local council: that would make a real difference, insulating your home properly, or just by running an older EV (Like a £9k ancient 2017 BMW I3, which would need to be plugged in a "jaw dropping" twice a week)
More likely you'll see greater competition on charge rates: commercially and within car parks as a loss leader. (Office car parks, supermarket parking etc) At the end of the day, electricity is cheap, the only thing that makes it expensive initially is the install cost in the first place, thereafter it's cheap as chips.