The output power of a discrete assembly of n-Si-p-Si1-xGex (0 <= x <= 0.4) thermoelectric generators is measured as a function of load resistance. The influence of Ge content and nanowire structures on the performance of thermoelectric devices is evaluated in measurements around room temperature. The nanowire arrays are etched using a metal induced local oxidation and etching process, based on self-assembled Ag nanoparticles and HF. The use of nanowires and SiGe with dimensions smaller than 30 mu m, is beneficial for an improvement of, at least, a factor of 10 in the output power. However, better performance improvements can be obtained by optimising the thermal and electrical contact resistances at the interfaces. Optimisation of the electrical contact results in a performance boost by a factor of 25. (c) 2013 Elsevier Ltd. All rights reserved.