Retrofit the Twin Charger to get up to 58 miles of range per hour of charging. This has no effect on Supercharging but can speed charging with an HPWC or a high power J1772 charger.
The cost is $2,000 and includes both parts and labor. It is only available on the pre-refresh version of the Model S (cars made prior to April 2016).
The twin charger is out of production and may no longer be sold by Tesla. Check with service for the latest availability and costs.