I have a 2016 so windshield is not an issue. However, if your vehicle is registered the license plate should be read as you pass through and there should no penalty. I'm sure this has happened to me with my Harley and to the best of my recall I've seen the bike on my statement with no penalty assigned nor have I ever received a letter asking for payment.

 

I think depends upon your state

 

Here in MD (as in NJ, apparently), no penalty if the plate is registered to an EZpass account.

 

a) they have exterior transponders you can get that are meant to be mounted within the grill or under the car, etc. Here's your EZ pass: https://www.ezpassva.com/pdfs/bumpinstruc.pdf

b) on the west coast, the transponders are obsolete as the algorithm reads your plate and identifies your car, without the transponder (except for carpool lane toll areas, possibly)

I'm sending all mine back, as I quietly suspect the fastpass technologies have algorithms that have quickly surpassed the need for the capital investment of physical hardware, but there's a revenue line in their P&L that has them making a LOT of money off lost/non-returned transponders. They've accidentally set up a revenue stream around the hardware, and they can't ditch it now. I suspect the makers of the hardware themselves are lobbying hard to make sure this doesn't become public knowledge.

I'm not much of a conspiracy theorist, but it's patently obvious transponders are redundant, but there's enough of an economy around them, they are slow rolling their obsolescence.

 

As for me, I prefer using Uproad app in such cases without being afraid I can be charged for the tolls. It's a great tool, especially when you use toll roads a lot.