The efficiency of energy transfer in impact mechanisms, often referred to as impact engines, is of key importance for users of these devices, including hydraulic impact hammers. The choice of a method that allows for accurate and repeatable determination of the impact energy and impact frequency as a function of supply parameters (supply pressure, supply flow rate) is an important issue, ultimately enabling the assessment of the efficiency of these devices. For this purpose, an analysis was carried out of the available analytical, analytical-empirical, and empirical methods, along with their associated measurement systems. As a conclusion of this analysis, the authors proposed their own method, based on the empirical determination of the impact energy and impact frequency as a function of the supply pressure and supply flow rate. For the needs of this method, a concept, design, and documentation of a mobile measuring station were developed, enabling on-site testing of hammers at their workplace. Subsequently, using this station, appropriate tests were conducted. Based on the measurement results, the mechanical, hydraulic, and overall efficiency of the tested hammers were determined. This makes it possible to assess the operational quality of the tested hammers and to make decisions regarding their continued use or assignment for overhaul.