Our work on the physical properties of silver nanowire (Ag NW) networks is presented in this contribution and shows that such emerging transparent conductive materials (TCM) exhibit very promising electro-optical properties. In particular the optical transmittance of Ag NW networks is still very high in the near infra-red region which is not the case for other TCM such as Indium Tin Oxide. The present work demonstrates that high quality Ag NW networks can be obtained by using an optimal Ag NW density, together with a controlled annealing step. In-situ electrical measurements reveal the effects of thermal annealing on the electrical properties of Ag NW networks. This allowed us to determine the optimal thermal treatment and network density needed to obtain a high transparency along with a sufficient electrical conductivity. This work sheds light on the physical mechanisms behind the change in electrical properties of the specimen during a thermal annealing step. It also leads to an improvement of the electrical properties by optimising the association of the Ag NW density together with the effects of a controlled thermal annealing. In addition this investigation shows that the mechanical properties of such networks are compatible with applications requiring flexible substrate.