Since the commercial success of lithium-ion batteries (LIBs) and their emerging markets, the quest for alternatives has been an active area of battery research. Theoretical capacity, which is directly translated into specific capacity and energy defines the potential of a new alternative. However, the theoretical capacities relied upon in both research literature and industrial/commercial reports are somewhat superficial values. This tiny mistake has overshadowed the potentials of some battery systems while pictured illusive targets for others. Although the battery researchers know the basis of these theoretical values, misinterpretations have caused a severe misunderstanding in the market research and public reports. Therefore, it is of vital importance to highlight the appropriate theoretical capacities, which can make sense in the commercial batteries. The present comparisons clarify that there are serious misconceptions about the advantages and disadvantages of various electrode materials and batteries. From a theoretical perspective (regardless of the performance of available materials), the capacity advantage of Li–S and Li–O2 over LIBs is not as huge as what currently has been pictured. Replacing LIB with a counterpart sodium-ion battery (NIB) is accompanied by only 20% sacrifice in the overall capacity. And NIB has no considerable advantage over potassium-ion battery (KIB) in terms of specific energy.