A fuel cell system with stack redundancy, comprising: a fuel processing assembly adapted to produce a product hydrogen stream from a feedstock; and a fuel cell stack assembly adapted to receive at least a portion of the product hydrogen stream from the fuel processing assembly and to produce an electric current therefrom to at least partially satisfy an applied load having a magnitude, wherein the fuel cell stack assembly includes a plurality of fuel cell stacks that each have a maximum rated power output, wherein each of the fuel cell stacks has a plurality of operational states that include at least a first operational state, in which the fuel cell stack receives at least a portion of the product hydrogen stream from the fuel processing assembly and produces an electric current therefrom, and a second operational state, in which the fuel cell stack is not producing an electric current; and wherein the fuel cell stack assembly has a plurality of operational states that include at least a first operational state in which all of the fuel cell stacks are receiving at least a portion of the product hydrogen stream from the fuel processing assembly and producing an electric current therefrom, a second operational state, in which none of the fuel cell stacks are producing an electric current, and a third operational state, in which at least one of the plurality of fuel cell stacks is receiving at least a portion of the product hydrogen stream from the fuel processing assembly and producing an electric current therefrom, and at least one of the plurality of fuel cell stacks is not producing an electric current, wherein the fuel cell system further includes means for controlling the operational states of the plurality of fuel cell stacks. a fuel processing assembly adapted to produce a product hydrogen stream from a feedstock; and a fuel cell stack assembly adapted to receive at least a portion of the product hydrogen stream from the fuel processing assembly and to produce an electric current therefrom to at least partially satisfy an applied load having a magnitude, wherein the fuel cell stack assembly includes a plurality of fuel cell stacks that each have a maximum rated power output, wherein each of the fuel cell stacks has a plurality of operational states that include at least a first operational state, in which the fuel cell stack receives at least a portion of the product hydrogen stream from the fuel processing assembly and produces an electric current therefrom, and a second operational state, in which the fuel cell stack is not producing an electric current; and wherein the fuel cell stack assembly has a plurality of operational states that include at least a first operational state in which all of the fuel cell stacks are receiving at least a portion of the product hydrogen stream from the fuel processing assembly and producing an electric current therefrom, a second operational state, in which none of the fuel cell stacks are producing an electric current, and a third operational state, in which at least one of the plurality of fuel cell stacks is receiving at least a portion of the product hydrogen stream from the fuel processing assembly and producing an electric current therefrom, and at least one of the plurality of fuel cell stacks is not producing an electric current, wherein the fuel cell system further includes means for controlling the operational states of the plurality of fuel cell stacks.