Avista Corp. CEO Dennis Vermillion plans to retire at the end of the year. He will be succeeded by Heather Rosentrater, the energy company announced this afternoon. 

Rosentrater, who currently serves as Avista's president and chief operating officer, will be the first female CEO in the company's 135-year history. Upon assuming the role, Rosentrater will retain the title of president for the company and will take a seat on the company's board of directors. 

Rosentrater, 47, has worked for Avista for the entirety of her 28-year professional career. She began as a student engineering technician for Avista Labs in 1996, followed by a role as an electrical engineer three years later. 

Several leadership positions followed, where she managed departments and projects across both electric and natural gas divisions. By 2015, Rosentrater was named vice president of energy delivery. Four years later, her duties expanded as senior vice president of energy delivery and shared services. She moved into the C-suite a few years later as senior vice president and COO of the power company before adding the responsibility of president in 2023. 

Vermillion, 62, has been with Avista since 1985. He served in senior leadership positions for 24 years and has been the company's CEO since 2019, when his predecessor Scott Morris retired. 

Headquartered at 1411 E. Mission, in Spokane's University District, Avista is among the top 20 largest employers in Spokane County. As of last November, the company had 1,057 full-time equivalent employees in the county and about 1,750 workers companywide. The company has about 418,000 electricity customers and about 382,000 natural-gas customers in Eastern Washington, northern Idaho, and parts of Oregon.