Some Tesla owners in Florida evacuating ahead of Hurricane Irma found their cars capable of driving further between charges. According to Mashable and electrek, Tesla remotely unlocked the full battery capacity in Florida residents’ Model S and Model X vehicles with 75 kWh batteries that were previously locked at 60 kWh.

This was possible because Tesla sells these models at a lower price with the battery capacity locked at only 60 kWh, even though the full capacity is 75 kWh. The owner has the option to purchase an upgrade at any time; if they do, Tesla then remotely unlocks the software, giving the car roughly 30 additional miles per charge.

CNN reports that the free upgrade will remain available until Sept. 16.