Nearly 1 billion people still lack access to electricity. Another 3.5 billion people are connected to power that is unreliable or of poor quality. Yet data on electricity access and reliability remains coarse and incomplete. In collaboration with the World Bank and the National Oceanic and Atmospheric Administration (NOAA), we generate new High Resolution Electricity Access (HREA) estimates that identify the likelihood that a human settlement is electrified by monitoring and comparing time series data on nighttime light output across thousands of nights across the globe. This likelihood-based classification approach enables us to robustly estimate the proportion of the world living in electrified areas and the reliability of electricity supply over time. By leveraging advances in computational power, statistical algorithms, and new data from POPGRID and other sources on the location of human settlements, these high resolution data provide new tools to track progress towards reliable and sustainable energy access across the world.