Here is the WA state sales tax exemption form that can be used for purchasing charging equipment & installation and EV batteries. If going into Tesla to purchase an extra UMC or WC bring the form with you. And At this time, the exemption goes thru 2020. The law can be read here. EV vehicles with a base price $42,500 and below qualify for the first $32,000 to be tax exempt. This is on a rolling expiration that the DOR looks at the funds remaining quarterly and determines it's next expiration, but at this time looks like it will go thru mid 2019, but general reaction is it will be gone sooner. I have confirmed with the state the tax exemption does not need to take place at a WA Tesla store, so SW WA residents can take possession and have Tesla Portland calculate the correct sales tax. This can be read here. Currently there is an additional $100/year surcharge for registering an EV. July 2018 this will increase to $150/year. This is to take the place of the gas tax EVs are not contributing to. but no emissions testing! read more here. Puget Sound Energy customers can get up to a $500 rebate. It is limited to the first 5,000. More info and the submit tall forms can be found here.