Starting next week, Tesla will pilot a battery pack swap program with invited Model S owners. The selected owners will have the opportunity to swap their car’s battery at a custom-built facility located across the street from the Tesla Superchargers at Harris Ranch, CA.

Tesla intends the pilot program to test the technology and to assess demand.The Harris Ranch Superchargers sit off the I-5, the interstate highway connecting Los Angeles (and San Diego) with the San Francisco Bay Area and Sacramento in the north.

Initially, battery swap will be available by appointment and, according to Tesla, “will cost slightly less than a full tank of gasoline for a premium sedan”.

(Given the recent drop in the price of premium, that comparison may be a bit off.) Because more time is now needed to remove the titanium and hardened aluminum ballistic plates that shield the battery pack, the swap process takes approximately three minutes.

With further automation and refinements on the vehicle side, Tesla thinks that the swap time could be reduced to less than one minute, even with shields.

Tesla will evaluate relative demand from customers for paid pack swap versus free charging to assess whether it merits the engineering resources and investment necessary for that upgrade.

In June 2013, Tesla demonstrated a battery swap option for the Model S. The swap, which, similar to the Better Place approach, has the target vehicle drive over a pit for removal of the old and insertion of a new pack, then took about 90 seconds.

In addition to giving customers a rapid refueling option, battery swapping—if shown as based on real-world use—could ultimately result in Tesla maintaining its awards of a higher level of ZEV credits by the California Air Resources Board than if such a “fast refueling” option is not available or validated. Tesla sells those ZEV credits to other automakers.