We evaluate the impact of adding simple, accurate information to energy labels on consumers’ purchases through a large-scale field experiment with an online retailer of energy-using durables. In addition to the energy efficiency grades and energy usage information included in the standard EU labelling, we provide energy cost information at different aggregation levels. We find that providing lifetime energy costs leads to greater attention paid to low energy-efficiency class products during the search process and more purchasing, but has little impact on energy consumption in kWh or total cost of the products being purchased. Our results suggest that although customers do not understand the labels accurately, they still make nearly optimal decisions based on the coarse signals provided by labels. This is encouraging from a policy perspective because labels simplify the decision process and did not hurt economic-efficiency.