"Power Out" is a song off Arcade Fire's debut album, "Funeral", released in 2004.
The song was written by lead singer Win Butler and his wife Regine, along with former Arcade Fire member Josh Deu. It's lyrics take place in Montreal during the N. American ice storm of 1998, which left the city in darkness for nearly 2 weeks. Regine was living in Montreal at the time, and her experience inspired the tune. The lyrics are mostly metaphorical and ambiguous, which has led to speculation as to what it's message is. The lyrics are dark and have a theme of hompelessness, but don't let that stop you from diving in.
Here is their 2005 performance of "Neighborhood #3 (Power Out)" LIVE on Jools Holland: