## 1 Introduction  
Urban public transport is essential for carrying millions of people for their daily trips; however, it has a significant impact on greenhouse gas (GHG) emissions. Therefore, the electrification of urban buses is an efficient way to reduce emissions, as long as the supplied electricity is provided by low carbon energy sources. Additionally, electric buses (EBs) provide supplementary benefits compared to conventional buses such as a reduction of air pollution (fine particle matter), noise, and on-board vibrations [1]. Their maintenance is also easier and cheaper; however, the integration of EBs is a challenging procedure due to the increased power demand which adds additional stress to the electricity network. The location of charging infrastructures and charging periods can induce negative impacts on the utility grid. The three main locations for static-charging infrastructures are bus depots, line terminals, and bus stops. Most of the time, EBs are charged at the bus depot during the night [2]. Therefore, buses require sufficient battery capacity to perform their daily service of around 200-300 km [3]. The consumption of an EB varies between 0.76 and 2.79 kWh/km for a standard bus with an average of 1.65 kWh/km [4]. Therefore, at least 150 kWh battery capacity is required to complete the daily service. Suchan on-board battery pack weights approximately one ton considering the energy density around 150 Wh/kg for lithium-ion batteries. [PERSON] et al. have shown that an increase of the on-board battery capacity from 50 kWh to 400 kWh induces a raise in the bus' energy consumption by 25% [5]. A larger battery capacity will thus increase the available energy to perform a long trip without frequently charging the battery. However, it will also lead to an increased energy consumption due to higher bus weight. Battery capacity has also an impact on the capacity of passengers, as a higher battery capacity requires more space in the bus [6]. The TOSA project has shown that decreasing the battery capacity leads to a reduction on the battery weight by 5-7 tons, an increase of the passengers' capacity of 15-30%, and a reduction in the energy consumption of 10% [7]. Charging at the bus depot is usually performed once per daily service during several hours in the night at a power of 24-180 kW [1]. Currently, the majority of EB fleets is very small, around 15 EBs per bus fleet in Europe [2] and 6 in the United States [8]. However, in the future, the penetration of a higher number of EB fleets is expected, hence a higher amount of power consumption will most likely be observed during the night period. Although it is not a peak power consumption period for the utility grid, charging during the night might prevent transformers from cooling down and accelerating the degradation of these units. Alternatively, EB batteries can also be charged on-route at line terminals or bus stops (also called opportunity charging). Charging at terminals can occur around 20 times per daily service for a few minutes at a power of 150-600 kW [1]. On the other hand, charging at bus stops can occur around 200 times per daily service for a few seconds at a power up to 600 kW. From this perspective, the on-board battery capacity can be reduced with on-route charging, and it will lead to lower bus energy consumption. However, the short charging times imposed by passengers' transportation require high power to supply enough energy to the bus battery in a few seconds/minutes. A significant number of EBs in the fleets could impact the stability of the utility grid and create a risk of increasing the peak power consumption in the local area. A large number of EBs could also cause an overloading of utility grid transformers and induce the use of carbon-based fuel supplies, which release high GHG emissions. One solution to reduce the impacts on the utility grid is to produce electricity locally with photovoltaic (PV) panels. If the EBs charge during the daylight, the PV production can reduce the bus consumption peak.