Mainly published to reduce greenhouse gases emissions, new building regulations, leads to a constant improvement of building components such as building envelopes and static insulation. Although, the effectiveness and the behaviour of the air-conditioning plants, validated by commissioning procedures, affect greatly the energy needs in buildings, through ventilation requirements. The main work of Annex 40 of the International Agency of the Energy reports on "Commissioning of Building HVAC systems for Improved Energy Performance". The retro- and on-going commissioning of existing buildings HVAC systems can be achieved using many tools. In this annex, we focus on three which have several objectives and intervene in different phases of the commissioning process. One leads to the detection of faults whereas the others contribute to energy consumption evaluation. This paper presents a critical analysis of the various tools used and evaluates the potential of each tool in the commissioning phases under consideration, in order to determine the most convenient ones for the project in question. The work presented in this paper allows providing a helpful advice to the energy service company or to the technical and research institutes to determine the most adequate tool in terms of number of potential detected faults, precision in energy savings evaluation, and end-user's assessment. A critical analysis is presented to evaluate three of these tools and apply them to a real building. It appears clearly that the PECI Guide, developed for new construction, is very useful in retro-commissioning procedures. Moreover, Emma-CTA and its new versions (CITE-AHU, etc.) represent excellent fault detection tools and diagnosis tools of AHU. For energy savings, the IMPVP tends to become an international standard in measurement and verifications procedures for the ESCO, in order to evaluate energy savings following retrofit. The main issue of our work is to evaluate the operability, potential, time consumed, and results of these tools when used by the HVAC operation staff.