Systems, methods, and building block modules for modular power generation facilities are disclosed. A multi-stack modular power generation facility includes first and second pluralities of primary modules and first and second control systems. The first modules are positioned in a first stack to form a first vertical enclosure; the second modules are positioned in a second stack to form a second vertical enclosure; and the first and second modules each include gen-set modules, each with an engine-generator, and a switchgear module ganged to the gen-set modules. Each control system communicates with the respective gen-set modules to coordinate the engine-generators as a unit and to control the loading of each of the generators in response to a power load demand. The second plurality of primary modules are disposed immediately adjacent the first plurality of primary modules such that the second vertical enclosure abuts the first vertical enclosure.