ICTs account nowadays for 2% of total carbón emissions. However, in a time when strict measures to reduce energy consumption in all the industrial and services sectors are required, the ICT sector faces an increase in services and bandwidth demand. The deployment of Next Generation Networks (NGN) will be the answer to this new demand and specifically, the Next Generation Access Networks (NGANs) will provide higher bandwidth access to users. Several policy and cost analysis are being carried out to understand the risks and opportunities of new deployments, though the question of which is the role of energy consumption in NGANs seems off the table. Thus, this paper proposes a model to analyze the energy consumption of the main fiber-based NGAN architectures, i.e. Fiber To The House (FTTH) in both Passive Optical Network (PON) and Point-to-Point (PtP) variations, and FTTx/VDSL. The aim of this analysis is to provide deeper insight on the impact of new deployments on the energy consumption of the ICT sector and the effects of energy consumption on the life-cycle cost of NGANs. The paper presents also an energy consumption comparison of the presented architectures, particularized in the specific geographic and demographic distribution of users of Spain, but easily extendable to other countries.