The Energy Surge Season will begin on September 25th and run until November 8th, between Guild Seasons 13 and 14.
Between Guild Seasons 13 and 14, there will be a shorter standalone season with its own unique rules and schedule. This season will be called the Energy Surge season, as it will offer increased Invasion Days that are much closer together than usual, and with greatly increasing Season Point rewards and Siphoned Energy rewards each time. The Season Point Score will also qualify guilds to determine the Hideout HQ declaration rights for Season 14.
Visit the official forums for more information about the standalone season.