I had one 45 min phone interview, which included questions about my background, potential programs that might improve the organizations, some industry specifics, and one surprise math question. Then, about 2 weeks later, I was invited to come in for 4 one-on-one 30-min interviews and to give a 15 min powerpoint presentation in front of those 4 interviewers on "a technical topic of my choice." The final 30-min interview with the COO included a case study where I had calculate lifetime costs and discuss the factors involved in choosing between two PPAs (one solar, one wind).