Novel information technologies have the potential to improve decision making. In the context of smart metering, we investigate the impact of providing households with appliance-level electricity feedback. In a randomized controlled trial, we find that the provision of appliance-level feedback creates a conservation effect of an additional 5% relative to a group receiving standard (aggregate) feedback. Consumers with poor knowledge of appliance wattage respond most strongly to appliance-level feedback, consistent with the mechanism in our model. We estimate that a smart-meter rollout will yield much larger gains in consumer surplus if appliance-level feedback can be provided.