Developing Nearly Zero Energy Buildings (NyZEB) represents a path toward sustainable communities and is required by international regulations, starting with 2018. Combined measures for reducing the energy demand and increasing the share of renewable energy systems in buildings are very much investigated for different types of buildings. One specific case is represented by the buildings where - as result of the green energy policies - renewables are already installed, but the NyZEB status is not reached yet. These buildings are main candidates in getting this status as the initial investment required is significantly lower. A novel methodology is presented for this type of buildings aiming at identifying the optimal combination of actions to be taken for reducing the energy demand and developing optimized renewable energy mixes, integrating the existing ones, up to the (Ny)ZEB status. Following this methodology, a cases study is presented - the Solar House (low energy building with geothermal system and solar energy convertors) and the steps followed for reaching the Zero Energy Building standards are presented. Considering the current energy status of the building, the renewable energy potential and the costs, a tracked PV string array is proposed to be added and the steps in design optimization are outlined. (C) 2013 Elsevier B.V. All rights reserved.