Grid-level storage of renewable energy using electrolytes from seawater is a platform technology with multiple byproducts and use-case scenarios. The core application is to provide load-leveling for intermittent sources such as wind and solar. Membranes which conduct sodium to a cathode for energy storage yields chlorine gas, which can be sold. Discharging stored sodium produces electric power, and also sodium hydroxide and hydrogen gas. Hydrogen can be sold, or combined with stored chlorine gas in a HCl fuel cell to boost the round-trip energy efficiency of the seawater flow battery system. Sodium hydroxide can be used in alkaline exchange membrane fuel cells. The brine from conventional desalination can be processed to produce sodium metal plus fresh water which can be released into the marine environment. Sodium metal extracted from the cathode can be used as an energy vector which, when combined with water, produces hydrogen on-demand for use in variable load applications such as fuel cell vehicles. This paper explores the energy and mass balances of these various use-cases, illustrating which combination of them has economic viability in one or more applications.