Savvy EV owners know they can charge their vehicles without spending a dime by taking advantage of free charging stations. But an increasing number of states are imposing excise taxes that could pull the plug on these no-cost fuel-ups.

In May, Georgia Gov. Brian Kemp signed a law that will tax electricity generated at public charging stations at a rate of 2.84 cents per kilowatt-hour, starting in 2025. 

Proponents say it makes up for the fact that EV drivers don't pay the gasoline tax that helps fund road maintenance.

"Georgia has a reputation for great roads, road maintenance, and for bridge repair and very continual bridge updating. That's not free,"  Rep. Rick Jasperse, chair of the House Transportation Committee, told Route Fifty.  "We just want everybody using the road to pay their fair share."

The law also requires EV drivers to pay for how much electricity they use, rather than the amount of time they're plugged in, as mandated by President Joe Biden's $1.2 trillion infrastructure deal.

Gas tax revenues, both state and federal, have been on the decline for years. The rise in electric vehicles is only a relatively minor factor, though: Improved fuel efficiency has meant motorists are filling up less often, and lawmakers have been slow to reconfigure how gas is taxed.

To address the funding gap, at least 33 states have added an annual registration fee for electric vehicles -- ranging from from $50 in Colorado to up to $225 in Washington state -- that is on top of standard car registration and renewal fees. 

Some states have launched pilot programs that replace the flat charge with a road usage fee, based on how many miles you drive in a year.