Finding cost-optimal solutions towards nearly zero energy buildings in accordance with European Energy Performance of Buildings Directive is a challenging task: in order to reach the 20-20-20 targets the European energy policy introduces new ambition levels regarding the diffusion of nearly zero energy buildings and the methodology for cost- optimal levels for energy performance requirements. These new concepts permit to carry out the thermal design of a building as a compromise between energy saving, cost saving and energy requirements. In according to these elements, the goal of this work is to analyze a residential Reference Building by its energy and financial performance evaluating different design options for the building envelope and the HVAC systems which are combined in several energy packages.