This work involves preparing a basis for the company Riksbyggen AB and the housing association Brf ASEA-Stan for a possible installation of solar panels on their apartment building on Relävägen 5 (722 24) Västerås. As the company has already installed solar cells on other apartment buildings, a comparison will also be made between the various apartment buildings and what it means in terms of production to install solar cells on Relävägen 5 (722 24) in Västerås. Payoff time and the placement of the solar panels are further factors that have been taken into consideration when designing the solar system at Relävägen 5. From the results a conclusion was made that the apartment building electrical usage may be affected positively by an installation of solar panels. This is because in the summer the building can be self-sufficient while in the winter the building won’t need to buy as much electricity even though the sun hours are very low. The slope of the solar cell system is crucial for the electricity production for an apartment building, which reflects the work’s comparison of the slope and its differences. Interviews, study visits and simulation programs are examples of methods used during the work to facilitate the design of the solar cell system.