Average US driver goes 13.5kmi/year. This is about 36mi/ day. Most cars will get 2-4 mi/kWh, so this is about 12kWh/day. Average charging of like 8 hours gives about 1.5 kW over night. This isn't nothing, but it's a bunch less than people think about. I was regularly driving off of what a standard 120v socket would supply. (Not right now, because I can no longer charge overnight, due to a recall)

Also grid power can become more green if more green sources come online, but your gas powered car will always be gas powered.