Financial efficiency of retrofitting actions of dwelling stock is always difficult to evaluate. Even if retrofitting market is not driven by financial profitability, evaluation of any efficiency programme is necessary and relies primarily on energy saving calculations and costs assumptions. The main question is the accuracy of chosen assessments that depend to a large extent on available data and sources. In this paper, we discuss how arguable is an evaluation with 5 different methods of energy savings evaluation and 5 different sources of cost data. For each considered retrofitting action (3 for dwelling envelope, 2 for space heating system, and 1 for domestic hot water generation) 5 different financial indicators are calculated. Large number of results (900 data) allows discussion on data, sources and methods accuracy. Ranking of retrofitting actions and influence of chosen indicators are also discussed. Finally, the impact of energy saving evaluation methods and cost data on the cost and energy savings variability of retrofitting program is calculated.