To continually monitor decarbonization progress and track emissions in the electricity sector, new tools are needed. Since the availability of solar- and wind-based electricity generation varies throughout the day and in space, so does the carbon impact of drawing electricity from the grid. By leveraging publicly available plant-level electricity and emissions data on the hourly operations of the US power system, we traced embodied emissions flows in hourly electricity exchanges between the US electric balancing authorities in 2016. The dataset we built can be used to provide better carbon accounting tools and to estimate the environmental footprint of electricity consumption. In the California Independent System Operator (CAISO) for instance, electricity imports represented 28% of consumption in 2016, while 40% of the carbon released to the atmosphere to meet consumption was released outside the CAISO. To enable the real-time tracking of power system emissions, a second hourly emissions estimation method was subsequently developed that relies on hourly electricity data and technology-specific emissions factors. This visualization is updated hourly. These hourly electricity data were also used assess the impact of high shares of renewable generation from water, wind and sun on fossil generation sources and on exchanges.