Decarbonizing California: What to Know About the Advanced Clean Fleets Initiative

Key points

  • The Advanced Clean Fleets (ACF) rule is a first-in-the-world requirement intended to help California fully transition trucks and other operational vehicles away from gas and diesel fuel to fully zero emissions by 2045 "everywhere feasible"
  • Pairs with the Advanced Clean Trucks (ACT) rule that sets a timeline for manufacturers to phase out most gas- and diesel-powered heavy-duty vehicles by 2035
  • The ACF applies to various truck categories, including medium-duty and heavy-duty trucks
  • Expected to generate $26.6 billion in health savings from reduced asthma attacks, emergency room visits, and respiratory illnesses
  • Factors in potential cost savings for fleets and accelerated benefits for California communities

California, known for its commitment to environmental sustainability, has taken a groundbreaking step towards reducing greenhouse gas emissions and improving air quality. On April 28, 2023, the California Air Resources Board (CARB) unanimously adopted the Advanced Clean Fleets (ACF) regulation to transition California fleets to zero-emission medium- and heavy-duty vehicles, marking the world's first mandate to phase out gas- and diesel-powered truck sales.

The ACF rule complements the Advanced Clean Truck (ACT) regulation adopted in 2020, which set a timeline for vehicle manufacturers to phase out most vehicles powered by fossil fuels and ensure that zero-emission vehicles become available. The goal is to reach 100% zero-emission vehicles by 2045 with earlier targets for market segments such as drayage trucks, first- and last-mile delivery, garbage trucks, local buses, and utility and government vehicles.

Starting next year in 2024, under this new regulation, high-priority fleets which include large fleets and local, state, and federal government fleets will begin transitioning to zero-emission vehicles. From 2024 to 2035, the percentage of zero-emission truck sales required progressively rises.

For example, last-mile delivery and yard trucks must transition by 2035, work trucks and day cab tractors must be zero-emission by 2039, and sleeper cab tractors and specialty vehicles must be zero-emission by 2042.

CARB estimates that by 2035, 2045, and 2050, the ACT and ACF regulations will result in approximately 510,000, 1,350,000, and 1,690,000 zero-emission vehicles (ZEVs) in California, respectively.

Exemptions based on available technology are available for fleet owners. Fleets can also opt for a phased transition through the optional ZEV Milestone Phase-In program, allowing flexibility to continue using combustion-powered vehicles as needed.

To support the transition, California agencies have committed to the Zero-Emission Infrastructure Joint Agency Statement of Intent. This collaboration will plan, develop, deploy, and fund the necessary electric charging and hydrogen stations to achieve zero emissions by 2045.


What is the compliance timeline of the Advanced Clean Fleets (ACF) rule?
There is more than one way to achieve compliance with the rule, the milestones below are one of them. The following timelines are based on the vehicle model year and are divided into milestone groups.

Is there a list of consulting companies / service providers that CARB provides?
CARB partners with CalSTART to provide interested fleets with free one-on-one consultation services to help transition to zero-emission through the Cal Fleet Advisor program ( This program is not for regulatory compliance or reporting, however. For regulatory compliance, contact to ask questions about regulatory compliance, and for technical assistance questions about the TRUCRS reporting system.

What is a "high priority" fleet under Advanced Clean Fleets?
CARB defines a high-priority fleet as one belonging to a company with $50 million or more in revenue OR operating or controlling 50 or more trucks over 8,500 pounds. Yard tractors and out-of-state vehicles are included in this count.

Can fleets achieve compliance by leasing EVs from 3rd party owners?
Leased vehicles are considered "owned" by the fleet owner/lessee if the lease is for more than one year, and the terms of the lease agreement specify the lessee is responsible for compliance with state laws. If that is the case for any leased ZEVs, they would count toward the fleet owner/lessee's fleet, otherwise they count toward the lessor's fleet.

Under the milestone compliance options, how does the engine model year differ from the vehicle model year?
The ZEV Milestone Option does not use the engine or vehicle model year for any compliance determinations; only the Model Year Schedule has compliance based on the vehicle's engine year or access to provisions based on the vehicle's model year. In general, vehicle engines are a year behind the model. For example, a 2025 model vehicle will likely have a 2024 model year engine. Learn more about CARB's information regarding engine labels and emission control labels.

Do gas-to-electric vehicle conversions count towards compliance?
Yes, as long as the converted vehicle meets the definition of ZEV as defined in the regulation language.

Can small businesses benefit from the ACF rule?
Yes, the ACF rule aims to support all fleet operators, including small businesses, in transitioning to clean fleets. Financial incentives and programs are designed to assist businesses of all sizes in the adoption of sustainable transportation solutions.

Will the ACF regulation only apply to fleets with large vehicles?
The regulation covers vehicles class 2b and above, but it also encourages smaller fleets to adopt clean technologies voluntarily.

How can I afford to be compliant with the ACF?
To support compliance with the ACF regulation, financial incentives, grants, and funding opportunities are available. These resources aim to alleviate the financial burden associated with purchasing zero-emission vehicles and developing the necessary charging or refueling infrastructure. Below is a short list of funding opportunities for business fleets.

CARB approved $2.6 billion to assist in accelerating the fleet transition, with the following funding options:

  • Clean Vehicle Rebate Project (CVRP): Offers rebates for purchasing or leasing eligible new zero-emission vehicles (ZEVs).
  • Clean Cars 4 All: Provides incentives to replace older, high-polluting vehicles with cleaner options, including EVs.
  • California Clean Fuel Reward: Gives point-of-sale discounts to buyers or lessees of new ZEVs.
  • Community Air Protection Program: Focuses on reducing air pollution in disadvantaged and low-income communities, including through the deployment of EV infrastructure.
  • Hybrid and Zero-Emission Truck and Bus Voucher Incentive Project (HVIP): Provides vouchers for the purchase of new clean trucks and buses.

What is the credit trading and selling option?
Fleet owners meeting early compliance targets can earn additional credits. These credits can be traded or sold to other fleet owners to assist them in meeting their compliance requirements.

Our team at Merge can help identify the requirements and low-risk options for introducing EVs into your business fleet. Get in touch with us today to learn what's available for your business.

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