Environmental Entrepreneurs (E2) & E4TheFuture, Dec. 2016.
http://www.e2.org/wp-content/uploads/2016/12/EnergyEfficiencyJobsInAmerica_FINAL.pdf

"This analysis finds that most energy efficiency workers are at small companies with 25 or fewer employees. Forty percent of energy efficiency companies focus on installation, while another 26 percent are in trade and distribution. The remaining firms are in professional services, engineering and research, and other categories. The majority say they depend on the energy efficiency market for at least half of their revenue."

See data by State in Appendix:
Washington - pp. 116-117
Oregon - pp. 96-97
Idaho - pp. 48-49