I can't reproduce that error. For me the time only halves if I have Twin Chargers selected (as expected).I think there is a bug in the calculator: Selected a distance (100 miles) and a single charger. The charging time cuts in half between the 240v-40a Nema 14-50 and the wall charger. This seems correct except that the wall charger with a single charger in the car is also rated at 240v-40a and should be taking the same amount of time. Both options correctly show 240v-40a. It is just that the charging time should be the same between them.