We conduct a field experiment on electricity conservation to study whether revealing both the competitive state and the social state in a group contest affects individual beliefs and efforts. Our experiment randomizes group composition, participation, and types of information received in the contest. We find that contestants without feedback about relative performance had difficulty assessing their group’s competitive status, and laggards within a group tended to be overconfident about their relative contribution. In addition, we find that contestants receiving both competitive and social information were more likely to have correct beliefs about their positions during the contest and exerted the most effort. Meanwhile, contestants receiving no performance feedback did not behave differently from those who did not participate in the contest. Overall, contestants reduced their energy use by 10% during the contest. Our results support the notion that providing feedback is important in a group contest.