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King County Metro is leading the transit industry—and the country—by being an early adopter of a battery-electric bus fleet. Electric buses produce no exhaust, are quieter, and have the opportunity to lower operating costs. Metro has committed to move to a 100% zero-emissions fleet powered by renewable energy no later than 2040.

Frequently asked questions

Metro is committed to a 100% zero-emissions fleet by 2040. Over the next 20 years, we expect to have approximately 2,200 battery-electric and electric trolley buses.

A zero-emissions fleet benefits the community, riders, and employees by eliminating greenhouse gas emissions and improving air quality. Additionally, the program aligns with broader King County equity and social justice goals around the Strategic Climate Action Plan.

Metro operates a fleet of over 1,600 buses. Currently, there are 185 zero-emission buses, which includes 174 electric trolley buses that use overhead wires, and an additional 11 battery-electric buses with charging stations at the Bellevue Campus and Eastgate Park-and-Ride.

In 2018, Metro began leasing 10 battery-electric buses from three manufacturers (two 40' buses from Proterra, two 40’ and two articulated 60’ buses from New Flyer, and two 40’ and two articulated 60' buses from BYD) for testing during 2019-2020.

These buses can go up to 140 miles on a single charge, which would cover 70 percent of Metro’s routes. The current testing will provide data on performance and reliability in our geography, traffic and weather as well as battery size, technology limitations and charging methods. Metro’s plans to order 120 battery-electric buses in 2020 will be informed by the results of this testing.

The main types of charging methods include fast charging, also referred to as in-route or opportunity charging, which allows buses to quickly (for example, 20 minutes) be charged in between routes and before returning to the base. Slow charging, also referred to as overnight charging, takes longer (hours) and requires that the bases have the charging infrastructure needed. Metro is still exploring the best charging methods to use.

While there are over 300 battery-electric buses in operation in the U.S., they are all deployed in small quantities and have been in service for only a few years.

There is insufficient data to draw conclusions regarding total cost of ownership, reliability and durability. These past deployments have focused on slow overnight charging or fast opportunity charging. Today we are seeing bus manufacturers offering larger battery packs but also combining them with opportunity charging capabilities to improve operational flexibility.

With current technology, battery-electric buses present some limitations that prevent them from directly replacing diesels and hybrids without significantly impacting operations in terms of availability and range, for example.

Metro will phase 120 zero-emissions buses into operations, starting in 2021 at the interim base at South Campus, followed by 250 buses at the South Annex base in 2025. Metro’s newest base, which will be built in south King County and is scheduled to open in 2030, will house, operate, and maintain 250 zero-emissions buses.

Like many other North American transit agencies, including Los Angeles, Vancouver B.C., Portland, and New York, Metro will be deploying a pantograph down solution, SAE J3105-1, seen at the right. At launch, chargers will be located at bus bases but future en-route chargers are also expected to be deployed. All chargers will be a mix of high power and low power, but the exact ratio is still being determined. Most chargers will be low power and used for overnight charging to manage the electrical load as well as lower costs.

Current testing supports routes up to 140 miles.

Metro is testing various battery sizes and cooling technologies. Currently, the 40-foot bus has a battery size of 350 KWh and the 60-foot articulated bus has a battery size of 500 KWh. The test buses have either a liquid or air-cooled battery system.

Metro is working closely with local utilities, and will most likely retain ownership of the electrical infrastructure.

The electrical infrastructure required to support battery-electric buses, including switchgears and transformers, is already deployed in other high electric-usage industries, including hospitals, large buildings and server farms. Metro has worked with Seattle City Light on a resiliency study of the feeders to the interim base to ensure power needs can be met.

The vehicles are still developing, but Metro has experience with new technologies such as diesel-hybrids and expects most technological issues will be resolved within one generation.


  • Metro is one of the first public transit agencies to adopt diesel hybrids.
  • Purchases new electric trolley fleet of 174 zero-emissions trolley buses.
  • Pilots three battery-electric fast charge buses on routes 226 and 241.
  • Commits to move to a 100% zero-emissions bus fleet powered by renewable energy.
  • Leases 10 battery-electric buses from three manufacturers for testing.
  • Orders 120 battery buses.
  • Rolls out electric bus operations from the interim base at South Campus.
  • Adds up to 250 additional battery buses to South Annex base.
  • Opens a new bus base in south King County to house, operate and maintain 250 battery-electric buses.
  • Metro will operate a 100% zero-emissions fleet (including battery-electric and trolley fleet).

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