Software engineers make decisions about the design of the software they are creating on a daily basis. These decisions may impact the application in terms of efficiency, usability, flexibility, etc. Different competing design decisions are therefore often evaluated in terms of their projected impact on quality metrics prior to implementation. Recently energy has become a concern for software systems, ranging from mobile devices to large data centers. Additionally, it has been recognized that the software executing on a computing device can have a significant impact on the devices energy consumption. This raises the obvious question of whether or not it is possible to reduce the energy consumption of a software system by the means of software design decisions. This work examines how the use of different servers impacts the energy consumption of a web application. Through a controlled empirical experiment we have discovered several important findings in this regard. The results indicate that the energy consumption of a web application can vary greatly depending on the web server used to handle its requests. Furthermore, different web servers are more or less energy efficient depending on which web application features are being executed. The paper details an analysis of the results of the experiment.