Based on lithiation to one lithium per transition metal, the gravimetric capacity of Nb18W8O69 is 164.1 mA×h×g -1 . A two electron 'multiredox' process, as observed in other niobium tungsten oxides 1 , would lead to 328.2 mA×h×g -1 . The high crystal density of 5.37 g×cm -3 should lead to electrodes with high volumetric density. Thus, (5 × 5) Nb18W8O69 is interesting as new anode candidate in its own right, but also to help understand the fundamental interplay of block size, composition, and electrochemical properties in the cs phases.