This thesis examines the transition from internal combustion engine (ICE) fleets to electric vehicle (EV) fleets. In particular, there is a focus on the economic effects from the point of view of the fleet owner, as well as overall environmental effects. This is accomplished through case studies involving different fleet-based business models and analysing the resulting effects of a transition to EV fleets. Furthermore, comparisons will be made between similar scenarios in two different European cities, namely Barcelona and Stockholm. Additionally, aid and incentives to motivate a change from ICE and EV fleets are explored in detail. The results show annual savings of 4,279.94 EUR/year and 6,352.33 EUR/year for taxi drivers in Barcelona and Stockholm respectively, and 6,405,121 EUR/year and 8,594,734 EUR/year for public bus operators in Barcelona and Stockholm respectively. Furthermore, the results show a reduction in local emissions of 12,727 kg CO2/year for taxi drivers in Barcelona and Stockholm, and 22,835,163 kg CO2/year and 19,134,464 kg CO2/year for public bus operators in Barcelona and Stockholm respectively. Finally, savings for delivery service fleets are shown to range from 18.25 EUR for 4,000 km up to 3,744.25 EUR for 50,000 km. The thesis concludes by acknowledging the large positive environmental effects, while also pointing out that despite the yearly economic savings, there is still a large financial burden associated with a transition to EV fleets. Ways in which this financial burden can be reduced include increasing the annual kilometres driven by vehicles in the fleet, and increasing the difference in cost between electricity and fuel prices.