Electric vehicles (EVs) have a high potential in reducing greenhouse gas emissions and are able to achieve other advantages such as a reduction in local air pollution and increasing energy security. As a result, EVs are rapidly increasing in popularity, electrifying the transportation sector. This poses a serious problem for the grid as existing distribution grids were mainly sized in the pre-EV era. In this paper, a method is proposed to determine the charging demand of future EV fleets in an office area and determine its flexibility potential. Office charging is studied as it differs from residential charging and a limited number of studies focused solely on office charging. The study is an empirical study and is based on analysing real transaction data of 42 EVs charging for over a year at Utrecht Science Park, Utrecht, the Netherlands, the considered case study. The transaction data allows for an examination of the impacts of future EV charging demand in an office area. The results based on a future scenario study show that in 2050, 4 out of 7 studied transformers are overloaded. This is followed by an analysis on the mitigation of the determined impact. This analysis also determined the flexibility in EV demand, around 50% of the EV demand can be delayed for more than 8 h. When this flexibility is used, overloading of 3 out of 4 transformers could be mitigated. This paper shows that placement of charging stations should be strategically performed, considering the capacity of the network and taking into account the forecasted load due to EVs charging.