I applied through college or university. The process took 1+ week. I interviewed at Opower in Jan 2013
Interview
Talked about my preview assignment. Was asked about my projects and works in software field. Was asked a question about "stack and queue". It was pretty smooth. I answered all the questions he asked. But we both knew I had no experience in this area.
The process took 1 day. I interviewed at Opower (Arlington, VA) in Jul 2010
Interview
Applied trough linkedIn and then was directed to jobvite. Posted a cover letter, HR called me, they assessed me with a little quiz and a programming homework.