Fleet-wide Electrification Impacts Assessment for the Valley Transportation Authority

Research output: NRELTechnical Report


This report explores the long-term electrification opportunities for the Valley Transit Authority (VTA). The potential for transit bus electrification at VTA as well as the economic impacts of partial and complete electrification are explored. We use the Revenue Operation and Device Optimization model to determine the optimal operation and lowest cost solution to achieve different levels of electrification. This study finds that around 70% of VTA’s transit bus fleet trips can be replaced with Battery Electric Buses (BEBs) today. The benefits and drawbacks of five methods for improving these results are discussed including 1) increase charger power, 2) purchase of larger vehicle batteries, 3) on-route charging, 4) purchasing additional buses and swapping them to enable the existing routes/blocks to be met, and 5) route/block redesign. A strategy is developed to enable full fleet electrification by increasing charger power or allowing intraday charging as a proxy for the options mentioned above. This method allows us to develop an understanding of the impacts and trade-offs of full fleet electrification. Two charging strategies are examined. Immediate charging, when the bus is charged as soon as it arrives, and smart charging, which uses a controller to determine the best times to charge to achieve the lowest operating cost. Smart charging is effective at reducing the peak power consumption, which can be reduced by between 31% and 65% compared to immediate charging. This translates directly to lower demand charges and lower costs for system upgrade. Given the cost and operating assumptions, the total lifetime NPV cost results show that smart charging scenarios are within ±4% of the lifetime NPV cost of the diesel-hybrid only (business-as-usual) scenario. The scenarios with full fleet electrification (i.e., including intraday charging) are 4% lower cost and those with partial fleet electrification (i.e., without intraday charging) are 2-3% higher. It is important to remember that the intraday charging scenarios do not include any additional costs to allow for additional charging to meet the routes. It was found that increasing the amount of PV at the yards can reduce the lifetime NPV costs. Conversely, adding storage does not necessarily reduce the lifetime NPV costs for a significant penetration of BEBs that are already optimally charging. Options to achieve this increased electrification potential are discussed in more detail in the report. We included as many details as possible at the time; however, there are some things to remember to provide context for these results. It is assumed that buses always operate as expected (e.g., there are no breakdowns). Additional costs to further enable electrification (described in this report as intraday charging) and electrical infrastructure upgrades are not included. These items have a wide range of variability from zero dollars to millions of dollars and can affect project economics. The hope is that this report will provide expectations for cost and impacts of bus electrification so we can have a more robust discussion with transit agencies and utilities to better characterize costs and opportunities to enabling greater electrification and minimize infrastructure upgrade costs.
Original languageAmerican English
Number of pages32
StatePublished - 2020

NREL Publication Number

  • NREL/TP-5400-77547


  • demand charge
  • electric bus
  • electrification
  • fleet-wide
  • lifetime cost
  • optimization
  • renewable integration
  • retail rate
  • smart charging
  • transit bus


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