Ameren is a regulated electric and gas utility holding company headquartered in St. Louis, serving customers in Missouri and Illinois. Ameren operates through three main subsidiaries: Ameren Missouri, which generates, transmits, and distributes electricity and distributes natural gas in Missouri; Ameren Illinois, which transmits and distributes electricity and distributes natural gas in Illinois; and ATXI, a FERC-regulated electric transmission business. Because Ameren holds exclusive franchises in its service territories, customers cannot choose a different delivery provider. As a regulated utility, Ameren earns a return on the capital it invests in electric and gas infrastructure — the "rate base" — with rates set by state and federal regulators designed to allow Ameren to recover costs and earn an allowed return on equity. Rate base growth is the core earnings driver: the more capital Ameren invests, the more it can earn. Ameren's growth is driven almost entirely by capital investment in grid modernization, electric transmission expansion, and new generation in Missouri — including natural gas, solar, battery storage, and eventually nuclear — to replace retiring coal plants and serve expected load growth from data centers and manufacturers. Ameren Missouri's current generation mix is primarily coal, but Ameren plans to retire all coal plants by 2042. The key earnings risk is regulatory lag — the gap between when Ameren invests capital and when regulators allow Ameren to earn a return on it.