Unless you plan on using the Superchargers Tesla is providing (so far all on North America continent, none in Hawaii) or installing one yourself, you probably don't need the twin chargers.
It seems it will be very rare to be charging at 80A/240V in Hawaii, and it isn't really necessary. On top of that, you have to pay an extra fee to activate the twin chargers on the 60kWh model.
Just to clarify, there is no extra fee to
activate twin chargers on the 60 kWh cars. There is just the initial cost. There is, however, a fee to build in the supercharging capability on the 60 kWh cars which sometimes was called an activation fee before details were known. It turns out the supercharging hardware is not something standard which can be activated. It actually has to be built in up front and is a paid for option on the 60 kWh cars.
Admittedly charging options can be confusing. This link is very helpful:
Tesla Charging | Tesla Motors. Here is a summary:
Single charger - standard equipment, onboard charger converts AC to DC, charges up to 10 kW = 31 miles per hour via a NEMA 14-50 receptacle, charges about 1/3 to 2/3 as fast at public J1772 charging stations.
Twin chargers - $1500 option, two onboard single chargers convert AC to DC, charge up to 20 kW = 62 miles per hour via Tesla's $1200 High Powered Wall Connector or high amperage J1772 public charging stations (none of which exist on Oahu at this time).
Supercharging capability - free for 85 kWh cars, $2000 option for 60 kWh cars, not available for 40 kWh cars, direct DC to DC, charges up to 90 kW = 300 miles per hour via Tesla's supercharging stations on the mainland.
Unless you have some unusual plan, you might save some money if you don't get the twin chargers.
I agree completely. On Oahu it would be an extremely unusual for twin chargers to be necessary. Also, it doesn't make sense for Tesla to install any supercharging stations on Oahu so paying extra for supercharging on a 60 kWh car is a complete waste of money unless the owner plans to move the car to the mainland at some point.