For all intents and purposes they are below the radar. From what I can tell just looking at California law (since so many folks are from their) their are quite a few incentive programs that encourage folks to get these kinds of vehicles. Everything from grants, to tax rebates, open use of the HOV lane regardless of occupancy, free meter parking (i suppose for recharging), 75% electrical energy rebates on home energy used to charge electric vehicles.

These are some excerpts from California State Law regarding fuel tax.

REVENUE AND TAXATION CODE
SECTION 8601-8621

8651. (a) An excise tax is hereby imposed for the use of fuel at
the following rate per gallon:
(1) Fourteen cents ($0.14) during 1990, on and after August 1.
(2) Fifteen cents ($0.15) during 1991.
(3) Sixteen cents ($0.16) during 1992.
(4) Seventeen cents ($0.17) during 1993.
(5) Eighteen cents ($0.18) on and after January 1, 1994.
(b) If the federal fuel tax is reduced below the rate of fifteen
cents ($0.15) per gallon and federal financial allocations to this
state for highway and exclusive public mass transit guideway purposes
are reduced or eliminated correspondingly, the tax rate imposed by
this section, on and after the date of the reduction, shall be
increased by an amount so that the combined state and federal tax
rate per gallon equals the following:
(1) Twenty-nine cents ($0.29) during 1990, on and after August 1.

(2) Thirty cents ($0.30) during 1991.
(3) Thirty-one cents ($0.31) during 1992.
(4) Thirty-two cents ($0.32) during 1993.
(5) Thirty-three cents ($0.33) on and after January 1, 1994.
(c) If any person or entity is exempt or partially exempt from the
federal fuel tax at the time of a reduction, the person or entity
shall continue to be exempt under this section.



8651.5. Notwithstanding the provisions of Section 8651, on or after
January 1, 1966 the excise tax imposed upon liquefied petroleum gas
shall be at the rate of six cents ($0.06) for each gallon of fuel
used. All references in this code to Section 8651 shall be deemed,
with respect to the rate imposed upon liquefied petroleum gas on or
after January 1, 1966, to also refer to this section. Neither the
tax imposed by this section nor the tax imposed by Section 8651 shall
apply to the use of liquefied petroleum gas in a vehicle during any
period of time for which the owner or operator of the vehicle has
paid the annual flat rate fuel tax as provided in Section 8651.7.



8651.6. Notwithstanding the provisions of Sections 8651 and 8651.5,
on or after January 1, 1971, the excise tax imposed upon natural gas
shall be at the rate of seven cents ($0.07) for each 100 cubic feet
of compressed natural gas used, measured at standard pressure and
temperature, and at a rate of six cents ($0.06) for each gallon of
liquid natural gas used. All references in this code to Section 8651
shall, with respect to the rate imposed upon natural gas on or after
January 1, 1971, also refer to this section. Neither the tax
imposed by this section nor the tax imposed by Section 8651 shall
apply to the use of compressed natural gas or liquid natural gas used
in a vehicle during any period of time for which the owner or
operator of the vehicle has paid the annual flat rate fuel tax as
provided in Section 8651.7.



8651.7. (a) The owner or operator, except an interstate user, of a
vehicle propelled by a system using liquefied petroleum gas, liquid
natural gas, or compressed natural gas may pay the fuel tax for the
use of those fuels by paying an annual flat rate fuel tax according
to the following schedule:


Unladen weight Fee
All passenger cars and other vehicles 4,000 lbs. or less .... $ 36
More than 4,000 lbs. but less than 8,001 lbs. ............... 72
More than 8,000 lbs. but less than 12,001 lbs. .............. 120
12,001 lbs. or more ......................................... 168

(b) The annual flat rate fuel tax described in subdivision (a)
shall be an annual tax. The annual period shall be that period from
the end of the month in which the tax was paid to the end of the
month prior in the following calendar year. When an owner or
operator elects to pay the annual flat rate fuel tax on more than one
vehicle, the owner or operator may request that the board prorate
the tax due on a vehicle added during the annual period, so that all
vehicles have the same annual period. In the year a vehicle is
added, the annual flat rate fuel tax for that vehicle shall be
calculated by dividing the fee set forth in subdivision (a) by 12 and
multiplying the resulting amount by the number of months remaining
before the beginning of the next annual period.
(c) The board shall adopt an identification procedure for vehicles
with respect to which the annual flat rate tax described in
subdivision (a) of this section has been paid.

8601. This part is known and may be cited as the "Use Fuel Tax Law."



8602. Except where the context otherwise requires, the definitions
given in this chapter govern the construction of this part.



8603. As used in this part "motor vehicle" includes every
self-propelled vehicle operated or suitable for operation on the
highway, except a vehicle used exclusively upon stationary rails or
tracks.


8604. "Fuel" includes any combustible gas or liquid, by whatever
name the gas or liquid may be known or sold, of a kind used in an
internal combustion engine for the generation of power to propel a
motor vehicle on the highways, except fuel that is subject to the tax
imposed by Part 2 (commencing with Section 7301) or Part 31
(commencing with Section 60001).
It does not include any combustible gas or liquid specifically
manufactured and used for racing motor vehicles at a racetrack.


8657. (a) Notwithstanding any provision of the Alcoholic Beverage
Control Act (Division 9 (commencing with Section 23000) of the
Business and Professions Code) any alcohol produced for use in or as
a fuel to propel a motor vehicle shall be taxed as fuel under this
part and shall not be subject to taxes under the Alcoholic Beverage
Tax Law (Part 14 (commencing with Section 32001)).
(b) The state requirements for determining whether alcohol is
produced for use in or as a fuel to propel a motor vehicle and not
for use as an alcoholic beverage shall be the same as the
requirements of the Bureau of Alcohol, Tobacco and Firearms of the
United States Department of Treasury under federal law.


Electric Vehicles are not included, and as fascinating as I find reading tax code. I'm going to give it a big shrug. The cost of energy has gone up 75% in the last year (MD decided to deregulate) so the era of cheap coal energy is going the way of that silly bird in a the clock. Honestly outside of the geeks I've met at alt energy festivals in this area I don't know a single normal person who drives a EV, [well nothing bigger than a golf cart anyways]. It would probably cost more to setup the govt. infrastructure then they would make in revenue.