The concentration of CO2 in the atmosphere has been rising rapidly for several decades. It leads to many negative consequences the most harmful among them being a global change of the climate and ocean acidification. Both of these events cause tremendous issues for the environment and threatens the existence of living species including human beings. Ever since the industrialization, the top contributor of all Greenhouse Gases (GHGs) happens to be human activities. Transportation, manufacturing, and electricity generation all heavily rely on fossil fuels, which are the primary sources of GHGs. In order to decrease CO2 emissions, it is essential to transform the current energy production and consumption techniques towards the technologies that do not pollute the atmosphere. There are many options available including nuclear and hydro stations, solar panels, wind turbines and geothermal. Although clean alternatives exist, the process of transitioning is not fast enough. Furthermore, the consumption of fossil fuels, e.g., oil, keeps rising year after year. This thesis work focuses on the reduction of CO2 emissions produced by residential sector. One way to achieve it is by using Home Energy Management Systems (HEMS). However, the adoption of such systems is not a wide-spread phenomenon. In order to promote the use of HEMS, this work proposes the development of a web-based application that plays the role of a frontend part for such systems. The application development consists of several phases, i.e., defining of the requirement, finding the right technologies, coming up with design structure, and building the application. As a result of this thesis, a prototype of the web application for controlling electricity consumption is developed. The proposed application offers various visualization widgets, promotes energy consumption plans to reduce emissions as well as energy expenses, and includes a notification system that supports sustainable choices. Besides, the application follows all modern web development practices, resulting in fast performance and intuitive user experience.