Powering Seattle fleets: A charging infrastructure strategy for battery electric medium- and heavy-duty vehicles

The electrification of Class 4-8 medium- and heavy-duty vehicles (MHDVs) is projected to accelerate through 2040 due to reduced costs, improved technology performance, and a favorable policy landscape. Seattle City Light (SCL), the municipal electric utility of Seattle, Washington, is responsible for ensuring that there is sufficient infrastructure and grid capacity to meet the future energy requirements of transportation electrification in the Seattle area.

This report serves to inform the development of SCL’s charging infrastructure strategy as it plans for upcoming MHDV electrification. Key players expected to lead the surge in electrification are Seattle’s main bus transit provider, King County Metro, and the robust local freight and distribution network serving the Ports of Seattle and Tacoma. The researchers incorporate local vehicle activity data and other information specific to the Seattle area to determine future charging needs within the SCL service territory from 2025 through 2040. The modeling predicts:

  • There will be a marked increase in MHDV charging stations needed around 2030 based on fleet electrification goals and supporting regulation.
  • The total charger nameplate capacity and peak loads in the SCL service territory will increase over three orders of magnitude between 2025 and 2040.
  • MHDV charging demand will likely be concentrated in the southern part of SCL’s service territory, where most warehouse and distribution centers are located, increasing the need for additional local distribution grid capacity. This industrial zone will likely require assessment in the near term to determine needed substation upgrades and investment in existing infrastructure.

Based on the modeling predictions and discussions with SCL staff, the report offers the following recommendations for SCL to consider as it formulates its charging infrastructure strategy:

  • Gathering information from fleets, especially those with known transition plans
  • Prioritizing infrastructure development in “no regrets” zones where there is a known need for future grid capacity
  • Addressing potential grid capacity constraints
  • Preparing for opportunity and en-route charging needs
  • Accounting for the needs of fleet customers in ratemaking
  • Adjusting internal operations to reflect changing business needs
  • Advancing equity goals in infrastructure planning