Hi. I have a Vauxhall Ampera and soon after buying it swapped to E7 so I could charge it overnight as cheaply as possible. The fitting of the new E7 meter was free with EDF and there was no tie in period. I then swapped to Sainsburys energy , their E7 rate is 5.1 p/unit and daytime rate 12.5p/unit which is actually cheaper than the old EDF rate! So win win. My E7 to normal use is around 50:50. It definitely pays to shop around.