This thesis is part of a long-term research project and covers the installation of a measurement system, the sensor data processing and as a major part the evaluation of the energy efficiency for a sucker rod pump producing a sample oil well. The selected pumping unit is equipped with sensors covering the electric power feed and the movement of essential rotating parts. As a first step, the rotation sensors are used to evaluate the accuracy of a published kinematic model describing the movement of a pumping unit. This is used as a foundation to analyze the counterbalance of the surface structure and find an optimum balancing. By combining the data from newly installed sensing devices with volumetric production data and commercially available sensors for measuring the polished rod load and wellhead pressures, the electric, mechanical and hydraulic power is calculated. By the investigation of the counterbalance, the necessary parameters for lowering the net torque acting on the gearbox below the critical rating can be found. By measuring the revelations of the reducer and the motor sheave, the actual slip of the V-belt is identified and matches the values from literature. The evaluation of the powers revealed a low overall efficiency for the sample well. Detailed analysis of the single efficiencies makes it possible to spot the major occurrence of losses in the downhole section. The low lifting efficiency hereby is linked to a low volumetric pump efficiency. By excluding gas interference and pump-off conditions as reasons, a high slippage rate at the clearance between the plunger and the barrel is assumed to cause the low pump efficiency. The results in this work can be used to resolve the low efficiency of the sample well but should as well be a guide for further efficiency evaluations of sucker rod pumps