The objective of this article is to create a mathematical model based on the analysis of the life-cycle cost of a passive house, including its technical design variations. In this study, we analyzed 14 types of houses derived from the design of the passive house POLITEHNICA; every house was differentiated by the type of renewable solution used (EAHX, GHP, solar collectors, PV panels) or by the insulation thickness, and it was compared with H12, a standard house with classical HVAC systems and a thermal insulation of 100 mm. The houses were compared according to criteria of economic performance throughout their life cycle. It was found that the additional investment in an energy efficient house can be recovered in 16-26 years, 9-16 years and 16-28 years if the replaced HVAC system is classical gas fuelled, electric or district distribution. A sensitivity analysis is performed which revealed the influence of the price of electricity and PV panels. The classification system made the decision-making process easier for a possible investment in a solution. This classification system showed that the first three recommended solutions for investment are the houses H14, H17 and H20. (C) 2014 Elsevier B.V. All rights reserved.