The current electrical grid is diversified — many input sources are combined to meet the ever-varying demands for electricity. However, in this loosely coupled, large-scale energy system, grid-priority for renewables can drive baseload, dispatchable power systems to follow the remainder of the grid demand by reducing power. Although new nuclear power plants can likely operate at a power level as low as 25 percent of their rated capacity (older plants may be limited to something closer to 50 percent of rated capacity), this is not a desirable operating mode from the perspective of optimizing the use of invested capital. Baseload power plants were not designed for an operational mode that incorporates significant power cycling. Cycling of either baseload nuclear or coal plants to accommodate the variable demand that results from the introduction of highly intermittent resources on the grid results in significant wear and tear on the plant systems, increasing operations and maintenance costs, and is potentially shortening the life of the plant.

A truly ‘hybrid’ system would be tightly coupled, requiring individual subsystems to be operated in an integrated fashion to respond appropriately to grid-level transients, while optimizing the energy use and minimizing cycling within the integrated system. This generalized architecture description then begs the question of what subsystems make sense in an integrated system. The vast possibilities for hybridization must be narrowed using established performance criteria to those that are technically feasible and can efficiently and reliably meet the need for a selected region or industrial application.