A “Cascading Startup Controller” provides various techniques for quickly and efficiently initializing grids of interconnected fuel cells. In general, the Cascading Startup Controller dynamically controls heat exchange between fuel cells in the grid to produce a cascading startup of the fuel cell grid via an expanding pattern of excess thermal energy routing from hotter fuel cell stacks to cooler fuel cell stacks. This expanding pattern of excess thermal energy routing is dynamically controlled via automated valves of a heat exchange grid coupled to the fuel cell grid to decrease a total startup time for fuel cell stacks in the grid. Additional excess heat beyond that used to heat fuel cells to operational temperatures is then made available for a variety of purposes, including, but not limited to, preheating gas or other fuel for use by the fuel cells, local or community-based heating systems, heat-based energy cogeneration systems, etc.