The distance a car goes between top ups is different for most people. I drive no more than 20 miles a day 99% of the time, so really I would only need something that gives 140 miles in a week to do me. On the odd occasions I go further than that in a day I am still under 140 miles return. On the really, really rare occasions I go further than 140 miles a day I am ready for a spot of lunch well before 140 miles so no problem charging my Tesla model X whilst eating my cucumber sandwiches lol.