Sorry, I should've been more clear.
The battery in my car has a 33kW capacity.
The charger I have installed on the side of my house is rated at 7kW. That means the charger (fancy name for a household plug socket really) is capable of delivering a maximum power of 7kW to my car. To do this, it needs a pretty fat cable, similar to a cooker or power shower (but bigger).
As I mentioned before though, the cost calculation is simple. You just multiply the battery capacity of the car by your unit cost of electricity. So if you were considering a Nissan Leaf with a 40kW battery then:
40kW x £0.29/kW = £11.60.
The charge capacity is only useful for telling you how long it takes to charge.
Normally, if you have a smart meter you can get yourself on an economy tariff which is cheaper at night to encourage you to charge overnight. I actually find this perfect as I wake up to a full battery every day.
As to whether you have the patience for charging, I guess it depends on how you use a car and the journeys you take. I bought mine when I had a 60mile/day commute (350miles/week) and it was perfect. My previous petrol car cost about £50/week. My EV only has a 130 mile range but I charged every night so wasn't an issue. At 5p/kWh it costs £1.65 to charge. My weekly fuel went down to less than £5 and I never have to go out of my way to visit a petrol station. It's completely personal but I accept the limitations of EV's because of the savings and convenience. I'm not sure I'll ever go back. If you can try one I'd recommend it as you might find them easier to live with than you think.