Electric Bus Basics

The Connecticut Electric Bus Initiative is a partnership between CTDOT, CT Department of Energy and Environment Protection (DEEP) and bus transit providers that showcases Connecticut’s commitment to providing a reliable, safe, sustainable, and clean energy transportation system.  Incorporating electric transit buses into a bus fleet transitions bus operations away from fossil fuels, reduces air pollution caused by diesel combustion and creates a brighter tomorrow for all of Connecticut’s residents. For the most up-to-date information on specific Electric Bus projects in CT, please visit the CTDOT Battery Electric Bus Initiative page.


Electric Bus Basics

A battery electric bus (BEB), also known as an all-electric bus (e-bus), uses batteries to power an electric motor for propulsion as well as the bus’s auxiliary systems. A BEB emits no tailpipe emissions for moving the bus (although the power plant producing the electricity may emit some pollution). Fortunately, the electric grid in Connecticut is very clean and, to ensure it becomes even cleaner, state regulators are working on an Integrated Resource Plan because without a clean electrical grid the emission benefits of electric buses would greatly diminish. 

In 2020, there are over a half-dozen BEB models commercially available. They typically have a greater initial cost compared to a diesel bus, but lower operating costs and by looking at additional BEB societal and operational benefits. 


Transit Bus Electrification is the Initiative’s Focus

Transit buses typically run cyclical, repetitive routes with predetermined schedules. Some buses cycle quickly, enabling frequent fast charges throughout the day. Others cycle more slowly, which works better with overnight charging at the bus facility.  Connecticut has selected to recharge the BEBs overnight at their respective bus depot while the electric grid has excess capacity.  Also, the many stops and starts of typical transit routes makes these vehicles ideal for electrification.  Electric buses are at an efficiency advantage over diesel buses when stopping because they can recoup kinetic energy losses via regenerative braking. They are also at an advantage when accelerating from a stop because electric motors operate optimally over a wide range of speeds vs. diesel engines that need to operate at higher RPMs.


Charging the Electric Bus 

The energy storage systems of a BEB are large (100-800 kWh) and the batteries have to be periodically charged to operate.  BEBs can be charged by plugging into a commercially available charging station typically located at the bus facility the bus returns to every night.  BEBs can also be charged en route using a variety of technologies that Connecticut may explore in the future, such as overhead chargers or inductive loop charging.  Each approach requires a different charging infrastructure system and impacts the BEBs lifecycle costs and benefits.  There are several plug-in chargers installed across each CTtransit division as well as the Greater Bridgeport Transit Authority. However, the CTtransit Stamford facility is currently in design for the first overhead pantograph fast charger in the state. This will allow BEBs to charge in a more efficient manner.  


CTDOT is currently working with the public utilities to determine the best course of action for a managed electric bus charging plan that would minimize impacts to the electrical grid and mitigate the impacts of peak demand charges on the operation of the electric transit buses.

Phased-In Rollout of Buses Across the State

Incorporating BEBs into the State’s transit bus fleet is a lengthy process that requires substantial capital investments, dedicated planning efforts and, the right partners to help ensure the program is a success.   Several transit operations across Connecticut have already attained funding and have begun the process of incorporating BEB’s into their fleet.



Electric Buses Offer Health and Societal Benefits

Connecticut’s bus network plays a crucial role in the lives of thousands of people, providing transportation for those who depend upon the bus for getting to work, to school, to medical appointments and, for those who cannot or do not wish to drive. The accessibility to clean, zero emission electric buses is an integral component of a just transition to clean transportation for communities and population sectors that have been historically more burdened by the adverse health effects of transportation pollution.    


Emissions Graphic







Connecticut’s Commitment to Electric Buses

Connecticut has identified electric vehicle deployment (both in the light-duty and heavy-duty sector) as among the primary solutions for achieving its statutorily required economy-wide greenhouse gas (GHG) reduction targets of 45 percent and 80 percent below 2001 levels by 2030 and 2050.


In 2019, the Connecticut General Assembly committed to electrify 50% of Connecticut’s light-duty fleet purchases and 30% of the heavy-duty fleet purchases, including transit buses by 2030. 

In July of 2020, Connecticut joined with other Northeast states to sign a Medium-Heavy Duty Zero Emission Vehicle Memorandum of Understanding to work collaboratively to advance and accelerate the market for electric medium- and heavy-duty vehicles, including school and transit buses.


Challenges Associated with Transitioning to Electric Buses: 

Battery electric buses represent a significant air quality improvement for both passengers and the people who spend considerable time living and working in the proximity of bus routes but they are also substantially more expensive than diesel transit buses and will require more thoughtful planning in order to be successful.

  • There are many capital/operating trade-offs
    • BEBs are significantly more expensive than diesel and hybrid buses
    • Charging infrastructure is expensive
    • Electricity is often cheaper than diesel
    • Potential for maintenance cost savings
  • Adequate planning is needed to ensure that the charging infrastructure is designed to support current and future deployments.
  • Connecticut’s electric utility rate designs need to be re-evaluated to mitigate the impacts of demand charges incurred when charging electric buses.
  • Energy resiliency measures, such as renewable on-site storage solutions need to be incorporated into electric bus planning efforts so transit agencies can continue to charge the buses during power outages, an increasingly regular event due to severe weather.


Finding Funding to Electrify Transit Buses

BEBs are substantially more expensive than other types of buses on the market but incentives are attractive right now and with the right infrastructure, electric bus fleets can generate substantial cost savings over diesel vehicles for transit agencies.  To achieve all the benefits that electric buses offer it’s important to be aware of current state and federal grants, bus warranties, and available financing options.  This is not a complete list but it is intended to help agencies begin to successfully navigate the funding available to electrify their transit operations and fleet.

Federal Transit Administration Low or No Emission Grant Program (Low-No)
This federal competitive grant program provides funding for electric transit buses and associated charging infrastructure.  The Low-No program is the largest battery electric bus grant program to date ($130 million of available funding announced in January 2020 (FTA 2020)) and many Connecticut transit agencies have applied and been awarded funding under this program.

The Diesel Emissions Reduction Act (DERA)
Requests for proposals for the National Clean Diesel Campaign and related information are posted on EPA's Clean Diesel Website. The program solicits applications nationwide for projects (including the electrification of transit buses) that achieve significant reductions in diesel emissions and exposure, particularly from fleets operating in areas designated by EPA as poor air quality areas.  DERA can also cover up to 45% of the total electric bus replacement cost, including charging infrastructure.

Connecticut DEEP also receives funds from the U.S. EPA through the State DERA Program to help mitigate the reduction of diesel emissions within our state.  Visit Connecticut’s DERA webpage for information on current grant opportunities.

Connecticut’s VW Mitigation Plan/Grant Funding
In 2018, over $50 million became available for various nitrogen oxide (NOx) mitigation projects, including bus electrification projects. While incentives under the VW Program are potentially more generous, many clean diesel projects that are eligible for the State DERA Program, are not eligible for VW funding. Visit Connecticut's VW Settlement webpage for more information on current grant opportunities.


Learn More About Battery Electric Buses

The Guidebook for Deploying Zero-Emission Transit Buses (2020)
The Zero‚ÄźEmission Bus Deployment Guidebook is a tool for educating transit agencies on current best practices for electric and fuel cell bus deployments and represents lessons learned from previous deployments, industry experts, and available industry resources.

Financial Analysis of Battery Electric Transit Buses (2020)
In this report, the modeling analysis strives to help transit bus fleets determine if battery electric buses would be cost-effective when compared to traditional diesel buses over their lifetime.


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