Power line communications (PLC) is a known low cost technology which is easily installed and extended to the various connections especially to areas with poor wireless coverage. Unfortunately, designers and users experience technical problems that arise from the difficulty of operating on a complex time varying medium and that limits the expected high throughput. Therefore, testing and understanding network dynamics of PLC systems before usage is a necessity. This paper presents the findings obtained from the experiments carried out in order to verify the throughput performance of PLC systems. Experimental measurements are realized in different testbeds, under different times and conditions, in order to achieve an idea of the practical PLC performance. Data obtained from the measurements have been stored and the throughput is analyzed by the help of software. Following, using distribution fitting methods, it is shown that the PLC throughput may be modeled by the extreme value distribution. Furthermore, adding a basic noise to the network, simply by lamps, results with a degraded performance. The noise changes the parameters of the derived distributions; a decrease in expected value and an increase in standard deviation are observed.