This paper describes the authors' experience in the assessment of laboratory activities based on an open source software package for power system analysis, namely, Power System Analysis Toolbox (PSAT). PSAT is currently used in several universities for both undergraduate and graduate courses. PSAT has also its own Web forum, which provides support to students and researchers all around the world, thus resulting in an almost unique example of ldquovirtual laboratoryrdquo over the Internet. This paper attempts to answer through a variety of real-life examples the following open questions: What are the practical and pedagogical advantages of using an open source software with respect to proprietary software for power system analysis? What happens if a power system virtual laboratory is freely available on the Web? What is the difference between a class-based and a Web-based virtual laboratory?