There are a few factors that affect charging rate at a Supercharger. First, charging your battery from 10% to 80% is quick while charging from 80% to 100% doubles the charge time because the car must reduce current to “top off.” Second, extremely low ambient temperatures and extreme battery pack temperatures lead to slower charging rates. Third, sharing a Supercharger (i.e. two cars plugged in to 1A and 1B) can slightly reduce the charging rate of one or both of the cars. For more information about Supercharger, visit the Supercharger page on tesla.com.