Social information programs are increasingly used to nudge behavioral change, but still relatively little is known about sources of heterogeneity in their impact. This paper examines whether individual values are associated with heterogeneous responses to social information. Using data from a large field experiment on household energy conservation, we combine electricity metering and survey data to study how environmental values affect the impact of the program. We then leverage the role of values by augmenting social information messages with an environmental self-identity prime. Results show that values are important drivers of heterogeneity. Moreover, enhancing social information by making environmental self-identity more salient boosts the social information impact, but only among individuals who acted pro-environmentally in the past.