The Washington laws have changed and there is no longer an official list. It simply states that the car must be able to be plugged in and that its base price before options is $42,500 or less. It is then exempt from state sales tax. This was put in place as of July 1, 2016 and will be available to the first 7500 takers.
From Section 4(f)
RCW 82.08.809
Exemptions—Vehicles using clean alternative fuels and electric vehicles, exceptions—Quarterly transfers. (Contingent expiration date.)
(f) The department of licensing must maintain and publish a list of all vehicle models qualifying for the sales tax exemption under this section until the expiration of the exemption as described in subsection (6) of this section.
The list: http://www.dol.wa.gov/vehicleregistration/altfuelexemptions.html