Taking the worst case, a Tesla Model S with the largest 90kWh battery pack, if charged from ‘empty’ would require 90kWh, which at a typical domestic electricity tariff of 14p/kWh will cost £12.60.
Perhaps more useful would be an assessment over time using the likely annual mileage.
A Tesla requires about 35kWh per 100 miles. So over a year where you drive 10,000 miles you would need 3,500 kWh per year – on average about 9-10kWh per day.
A smaller car, such as a Nissan Leaf requires about 28kWh per 100 miles and so would require about 2,800 kWh annually or about 7-8 kWh per day.
On a standard tariff at 14p per kWh the Tesla would cost you about £490 and If you have an Economy 7 tariff, where you are likely to pay about 7p per kWh, you will save £245.