Case study: The impact of electrification of Auckland’s bus depots on the grid

Auckland is one of 26 cities, as of September 2018, to have signed the C40 Green and Healthy Streets Declaration. As part of its commitment, Auckland has committed to only purchase zero-emission buses by 2025 and to transition its entire bus fleet to zero-emission technologies by 2040. As the price of zero emission buses continues to decrease and cities begin adopting zero emission bus technologies, cities are drafting roadmaps to guide the transition, including Auckland. The city is already trialling a few electric buses on its streets in 2018.

One of the most important challenges that cities, public transport agencies and operators face is in understanding the impact of the transition on the local electricity grid, particularly on peak power demand and grid upgrade costs for their bus depots. Grid costs (i.e. substation upgrades and cabling costs) can be a significant proportion of total costs, and converting a whole fleet can be challenging: for example, gradually introducing new electric buses in depots as old diesel buses are retired can be very costly to do, as any change to the grid infrastructure has high fixed costs. The report, developed for Auckland Transport, was prepared by Element Energy on behalf of the Financing Sustainable Cities Initiative, a partnership between the C40 Cities Climate Leadership Group and the WRI Ross Center for Sustainable Cities, funded by the Citi Foundation.

The main finding is that significant investment (up to NZ$32 million) in the Auckland electricity grid is required for the introduction of electric bus fleets. However, while the introduction of the electric buses will need to incorporate local grid upgrades, the higher levels of the distribution and transmission networks are likely to be unaffected. Moreover, the impact of the electrification of Auckland’s bus depots is expected to be much smaller than the effects caused by electric car uptake.

This case study illustrates Auckland's data-driven approach to bus electrification: for those still coming to terms with the complexity of the required adjustments to the electrical grid, it constitutes essential reading to understand how cities can assess the costs of depot electrification and plan a phased strategy for the introduction of zero emission buses.

For any questions about the report, please contact Anthony Courreges, Clean Transportation Finance Manager, at acourreges@c40.org.