Service Oriented Architecture (SOA) is an architectural paradigm that allows building of infrastructures for diverse application interaction and integration via services across different platforms, domains of technology and locations. SOA differs from traditional architectures, as it focuses on integrating capabilities that are distributed and implemented using a mixture of technologies. SOA provides a set of methodologies and strategies to accomplish interoperability and integration among different technology stacks.   Vattenfall is the fifth the largest energy supplier within Europe. Having operational systems in different countries brings the challenge of integrating all these distributed systems and this integration is a vital requirement for Vattenfall. The company is currently using Microsoft proprietary products to achieve integration across different technological platform, but requires a better integration infrastructure which is easily extensible and cost effective.   This thesis investigates the impact of implementing Service Oriented Architecture (SOA) using open source or proprietary software products within Vattenfall, from technological and financial perspectives. For this purpose, different technical and non-technical function blocks are identified which are essential for the implementation of SOA. These function blocks are mapped with SOA solutions provided by Red Hat’s JBoss Open Source SOA Platform and Microsoft’s SOA Platform. After mapping, a vendor specific technical and non-technical comparative analysis is carried out based on the function blocks, highlighting the strengths and weaknesses of each vendor.   Finally, an evaluation scheme is purposed based on the technical comparative analysis of vendors, SOA solution cost and SOA competence required. The results from this evaluation scheme are used to recommend the best solution vendor for Vattenfall Nordic. Moreover, this evaluation scheme can also be used to facilitate management in arriving at an appropriate decision about implementation of SOA, while remaining within their requirements and constraints.