Y. Gogotsi and P. Simon discuss the true performance metrics in electrochemical energy storage (EES). They argue that exceptional performance claims for electrodes in batteries and electrochemical capacitors (ECs) often fail when all device components are considered. Ragone plots, which compare power and energy densities, are commonly used to evaluate EES devices. However, these plots may not accurately reflect the performance of real devices because they often focus on the active material's properties rather than the entire device's weight and volume. For example, a carbon electrode with a high gravimetric energy density may have a much lower volumetric energy density due to its low packing density. This can lead to misleading claims about the energy storage capacity of ECs. The authors emphasize the importance of considering the entire device, including current collectors, electrolyte, and other components, when evaluating performance. They also highlight the limitations of using Ragone plots, as they do not account for factors like cycle life, energy efficiency, and cost. The authors call for standardized testing and reporting practices to ensure that claims about EES devices are accurate and comparable. They suggest that national and international testing facilities should be established to benchmark electrodes and devices, similar to those used for photovoltaics. Clear rules for reporting performance would help scientists, engineers, investors, and the public assess competing claims more effectively.Y. Gogotsi and P. Simon discuss the true performance metrics in electrochemical energy storage (EES). They argue that exceptional performance claims for electrodes in batteries and electrochemical capacitors (ECs) often fail when all device components are considered. Ragone plots, which compare power and energy densities, are commonly used to evaluate EES devices. However, these plots may not accurately reflect the performance of real devices because they often focus on the active material's properties rather than the entire device's weight and volume. For example, a carbon electrode with a high gravimetric energy density may have a much lower volumetric energy density due to its low packing density. This can lead to misleading claims about the energy storage capacity of ECs. The authors emphasize the importance of considering the entire device, including current collectors, electrolyte, and other components, when evaluating performance. They also highlight the limitations of using Ragone plots, as they do not account for factors like cycle life, energy efficiency, and cost. The authors call for standardized testing and reporting practices to ensure that claims about EES devices are accurate and comparable. They suggest that national and international testing facilities should be established to benchmark electrodes and devices, similar to those used for photovoltaics. Clear rules for reporting performance would help scientists, engineers, investors, and the public assess competing claims more effectively.