Keep in mind the people saying it is easy with there own vehicle have not experienced how the rental car companies make it so difficult to use your own Sunpass with a rental car. After all the hassle of going to three Walgreens to buy the Sunpass Mini and calling Sunpass to activate, going through the phone menu to finally get a real person on the phone they couldn't activate the Sunpass I just bought. Turns out the rental company only did half the work they needed to do to allow my Sunpass to work. I had to call the Rental Company back to get them to totally remove the license plate # from their account. Then call Sunpass back to get it activated. PIA.
The poster who asked is renting a car in FLL.
You want to activate it initially with your own personal vehicle. From then on it shouldn’t be an issue adding a rental car to your account. I’ve done it many times with vehicles & UHauls.
ADDITION: I was pretty sure I successfully used my SunPass recently in a Uhaul without registering the plate on my account. I just confirmed that it worked just fine. So I went to the SunPass website and found this in the rental vehicle section:
SunPass Customers
SunPass customers using a rental vehicle may have their tolls applied to their SunPass account. Customers with SunPass Portable transponders may use their transponders in their rental vehicles. It is strongly recommended that SunPass customers access their online SunPass accounts or contact the SunPass Customer Service Center to add the rental vehicle license plate to their account for the rental period. If the transponder is not in your vehicle or functioning properly, tolls from other agencies will not be posted to your SunPass account, and may be charged to you by the rental Service Provider. Please remember to remove your transponder upon return of the vehicle. SunPass customers that do not have their transponders in the vehicle are subject to the tolls, fees and charges set forth below and in their rental agreements.
Registering your plate on your SunPass account is recommended but not required. Your transponder will work and hit your account as long as it is functioning and properly placed.