In a residential field experiment at a large family housing community in Los Angeles, we demonstrate the use of health-based messaging as a powerful incentive to reduce energy use in the home and promote conservation. Building a wireless sensor network, we give consumers real-time access to detailed, appliance-level information about their home electricity consumption—through a website and weekly e-mails accessible on mobile platforms. Our results, based on a panel of 440,059 hourly observations for 118 residences over 8 months show that health-based messages, which communicate the public health externalities of electricity production, outperform monetary savings information as a driver of behavioral change in the home. Participants who received messages emphasizing air pollution and health impacts associated with energy use reduced their consumption by 6% over the experimental period as compared to the control group. Health messaging was particularly effective on families with children, who achieved up to 19.5% savings. Participants who received a message informing them about monetary savings increased their consumption by almost 1%. Our research advances our knowledge of effective non-price incentives for energy conservation.