*1.3. Limitations*

To better serve the purpose of identifying the underlying mechanisms, rather than giving an exact conclusion of a specific route, several simplifications are made. For example, the Total Cost of Ownership (TCO) model can calculate the cost of a non-integer number of buses. Such simplifications make it much easier to identify some general trends in cost changes and explain what causes them, but they also mean that the model is not intended to use when conducting the final and detailed cost analysis on a route. Rather, its purpose is to help determine which types of buses are interesting to investigate for a specific route, while the final analysis should be made with a more detailed bus-planning and cost analysis tool. The focus of the paper is to present the cost model, while analysis of bus routes is included only as examples of how the model can be used. The cost results presented should therefore not be seen as representative for all bus routes. The parameter values used in the examples are for a Swedish context and may need to be changed when analysing other bus routes.

The paper analyses the two charging strategies for electric buses: end-stop charging—when they are charged at the end stops on a route (included in the opportunity charging concept); and end-stop off-peak charging—buses charged at the end stops for the whole day except during the peak hours. The buses are also charged in the depot during night in order to be fully charged when they start operations. Both the electric bus charging strategies are compared with buses powered by biomethane or Hydrogenated Vegetable Oil (HVO), which is a biodiesel that can be used as a drop-in fuel in conventional diesel engines. In Sweden almost all buses run on biofuels, so we have not included diesel buses in the comparisons in Section 5. Diesel buses will have exactly the same costs as HVO buses, excluding the fact that the price of diesel fuel differs to that of HVO.
