Great breakdown, easy to understand and very informative. Being an electric car owner and also having solar panels, I have come to much the same conclusion as you. I charge my Leaf during the day in the summer when it's convenient, I have a 2.6 kWp system so I never reach the level needed for direct feed to the car but after 4 years I can tell it makes a difference. ! do have an off peak tariff, 5.3p kWh (with Ecotricity) so I generally charge at night. More recently I leased a Tesla Model S and my panels are woefully inadequate to deal with that, although in July this year I charged it from a 13amp socket (it would take about 40 hours to fill it) just for fun. A friend in Australia has 50 kWh battery system and a 15 kWp solar array on his rather large house in Adelaide, and 2 Model S' and a Roadster and an i3 in his spacious and spotless garage. He hasn't paid for electricity in 3 years. It's not fair. One day.