I'm also near Tampa, and I think our weather plays a major role in our EV efficiency. I do mostly local driving on my work day commutes and have been getting 64 EV miles consistently in the past 4 months I've owned my 2017 Volt Premiere.Well, here near Tampa most of my driving has been at 55mph but took 2 trips into south Tampa on I75 doing 70mph--a 52 mile round trip and still had 8 miles left. Granted, in the colder regions the available miles will be less. Now I'm up to 63 miles. Love this car.
The few trips I've taken on the highway were very sobering. Speeds of 70mph seem to suck the electrons out of my batteries very rapidly and there is no return with the lack of regenerative braking.