In this article, we present Power Agent—a pervasive game designed to encourage teenagers and their families to reduce energy consumption in the home. The ideas behind this mobile phone-based game are twofold; to transform the home environment and its devices into a learning arena for hands-on experience with electricity usage and to promote engagement via a team competition scheme. We report on the game's evaluation with six teenagers and their families who played the game for ten days in two cities in Sweden. Data collection consisted of home energy measurements before, during, and after a game trial, in addition to interviews with participants at the end of the evaluation. The results suggest that the game concept was highly efficient in motivating and engaging the players and their families to change their daily energy-consumption patterns during the game trial. Although the evaluation does not permit any conclusions as to whether the game had any postgame effects on behavior, we can conclude that the pervasive persuasive game approach appears to be highly promising in regard to energy conservation and similar fields or issues.