BACKGROUND: In March 2011, the Great East Japan Earthquake devastated several power stations and caused severe electricity shortages. This accident was followed by the implementation of policies to reduce summer electricity consumption in the affected areas, for example, by limiting air-conditioning (AC) use. This provided a natural experimental scenario to investigate if these policies were associated with an increase in heat-related mortality. OBJECTIVES: We examined whether the reduced electricity consumption in warm season modified heat-related mortality from 2008 to 2012. METHODS: We conducted prefecture-specific interrupted time-series (ITS) analyses to compare temperature-mortality associations before and after the earthquake, and used meta-analysis to generate combined effect estimates for the most affected and less affected areas (prefectures with >10% or