Ground clearance on the Model S is 6 inches according to Tesla[0] which puts it at par with a Honda Civic Sedan.
[0] http://www.teslamotors.com/sites/default/files/images/models...
[0] http://www.teslamotors.com/sites/default/files/images/models...
http://www.teslamotors.com/de_AT/forum/forums/air-suspension...