100% exemption for solar photovoltaic systems 10 or less kilowatts;
75% exemption for other qualified systems
In Washington State, there is a 75% exemption from tax for the sales of equipment used to generate electricity using fuel cells, wind, sun, biomass energy, tidal or wave energy, geothermal, anaerobic digestion or landfill gas. The tax exemption applies to labor and services related to the installation of the equipment, as well as to the sale of equipment and machinery. Eligible systems are those with a generating capacity of at least 1 kilowatt (kW). Purchasers of the systems listed above may claim an exemption in the form of a remittance. Originally scheduled to expire on June 30, 2013, SB 5882 od 2013 extended this incentive through January 1, 2020.
Solar energy systems 10 kW or less are eligible for a 100% exemption from sales and use tax. Purchasers of these systems can provide the seller with an exemption certificate to avoid paying the sales and use tax. SB 5882 expanded this incentive to include solar thermal systems capable of producing no more than 3 million British thermal units per day that use a solar collector or a solar hot water system. That same legislation extended the expiration date for this exemption to June 30, 2018.
Click [http://dor.wa.gov/Docs/Pubs/SpecialNotices/2013/sn_13_EnergyHeatSurvey.pdf here] for a special notice from the Washington State Department of Revenue about this program.
Systems greater than or equal to 1 kW