While looking into the option of reduced personal property tax rates for plug-in battery-electric vehicles (BEV), like the Nissan LEAF and Smart ED, I found something very promising for owners of these and other BEV. Apparently, Loudoun County, Virginia has set their purely electric vehicle tax rate at a mere $2 per $100 assessed.
Compare this to the car tax rate in Fairfax County, Virginia, which borders Loudoun to the East, which currently taxes at $4.57 per $100. In other words, register your 2012 Nissan LEAF SL in Fairfax County, your car tax for the first year will be $1,062.53. This includes the 1998 Personal Property Tax Relieve Act rate reduction for the first $20,000 of the vehicle, which in Fairfax County is set to 30%. That same car registered a few miles over would assess at $565 per year in Loudoun County, where the relief rate is currently set to 55%.
For reference, the standard vehicle personal property tax rate in Loudoun County for a non-electric vehicle is assessed at $4.20 per $100. Thus, in Loudoun County, an equivalently priced vehicle that was not fully electric would run you $1,186.50 in the first year.
Now, for a car to be considered registered in Loudoun County, it must in fact be garaged there most of the time. Historically, this has been an issue for states which border those with Vehicle Personal Property Taxes since in those cases the car owner could simply avoid paying the taxes entirely by registering the car in a new state, which most states are watching out for since that trick can be used by a lot of people. In this case, where it's just going across county lines, and only with respect to BEVs, the trick would be less common and therefore less worth enforcing with spot-checks of garages to make sure the vehicle wasn't regularly spending the night at the home of the person claiming to register it in a state other than the one in which he resides.