Medium- and heavy-duty standards

Ecology temporarily paused portions of some vehicle emissions standards in response to recent federal actions. Washington and 10 other states are challenging these actions in court.

During this pause we’re continuing our clean vehicles rulemaking and exploring new clean vehicle strategies for Washington through ZEVergreen. The ZEVergreen report was released in July 2026 and summarizes the feedback we received in 2025.

Washington adopted low- and zero-emission vehicle standards for medium- and heavy-duty vehicles through the Advanced Clean Trucks regulation in 2021 and the Heavy-Duty Low NOx Omnibus regulation in 2022. These regulations apply to vehicles with a gross vehicle weight rating over 8,500 pounds. There are some exceptions depending on which vehicle you're looking at, such as military tactical vehicles and authorized emergency vehicles. See the WAC 173-423-060 for more details.

If a manufacturer exceeds the zero-emission vehicle (ZEV) sales requirements for a particular model year, the credits they generate can be saved to comply in the future or sold to those who fall short of sales requirements. Ecology allowed manufacturers to start generating credits four years before Advanced Clean Trucks took effect in model year 2025. Fifty percent of a manufacturer’s requirements each year can also be met with credits generated by plug-in hybrid vehicles.

Manufacturers that miss the sales requirement for a particular model year have up to three full years to make it up.

Advanced Clean Trucks is a flexible policy that allows manufacturers to comply by selling increasing percentages of new medium- and heavy-duty ZEVs in Washington or purchasing credits generated by those who exceed sales requirements.

Advanced Clean Trucks sales requirements under vary by vehicle weight class:

Model year	Percent of class 2b-3 (8,501-14,000 lbs.) sales that must be zero-emission	Percent of class 4-8 (14,001 lbs. and up) sales that must be zero-emission	Percent of class 7-8 tractors (26,001 lbs. and up) sales that must be zero-emission
2025	7%	11%	7%
2026	10%	13%	10%
2027	15%	20%	15%
2028	20%	30%	20%
2029	25%	40%	25%
2030	30%	50%	30%
2031	35%	55%	35%
2032	40%	60%	40%
2033	45%	65%	40%
2034	50%	70%	40%
2035 and beyond	55%	75%	40%

The role of medium- and heavy-duty vehicles in Washington's greenhouse gas emissions

Motor vehicle emissions standards are a critical policy tool for addressing greenhouse gas emissions from the transportation sector. Transportation is Washington’s highest emitting sector, making up 40% of our total greenhouse gas emissions. And over 30% of those emissions come from medium- and heavy-duty vehicles even though they make up only about 10% of on-road vehicles in the state.

Fleet reporting

Large fleet operators were required to disclose information about the medium- and heavy-duty vehicles they use at the end of 2023. Planned rulemaking may authorize a new round of reporting in 2027.

Frequently asked questions

Under Advanced Clean Trucks, each manufacturer generates a deficit based on how many new internal combustion engine vehicles they sell. They must make up that deficit — or sales requirement — with credits generated through zero-emission vehicle (ZEV) sales.

Manufacturers can comply by generating their own credits or buying credits from others.

The regulation took effect with model year 2025, but manufacturers have been able to generate credits since model year 2021.

The table below shows ZEV credit balances in Washington state from MY 2021-2024. Note that non-tractor sales include all vehicles that earn credits for weight classes 2b-8, excluding semi-truck tractors, as these non-tractor credits are transferable between weight classes.

Reported ZEV credit balances in Washington state from MY 2021-2024

Manufacturer	NZEV credits (non-tractor)	ZEV credits (non-tractor)	NZEV credits (all tractor)	ZEV credits (all tractor)
Autocar	0.0	4.0	0.0	0.0
Blue Bird	0.0	40.5	0.0	0.0
BYD	0.0	11.5	0.0	42.5
Daimler	0.0	82.5	0.0	7.5
Ford	0.0	4,808.8	0.0	0.0
GM	0.0	223.2	0.0	0.0
Isuzu	0.0	0.0	0.0	0.0
Lightning	0.0	10.2	0.0	0.0
Lion Electric	0.0	4.5	0.0	0.0
Mercedez-Benz	0.0	16.0	0.0	0.0
Micro Bird	0.0	5.0	0.0	37.5
Navistar (now International)	0.0	79.5	0.0	0.0
Nissan	0.0	0.0	0.0	0.0
Orange EV	0.0	24.0	0.0	0.0
PACCAR	0.0	13.5	0.0	7.5
Rivian	0.0	1,316.0	0.0	0.0
Stellantis	0.0	19.2	0.0	0.0
Tesla	0.0	0.0	0.0	0.0
Volvo Trucks	0.0	0.0	0.0	122.5
Totals	0.0	6,658.4	0.0	217.5

No. Advanced Clean Trucks isn't ramping up more quickly in Washington than it did in California. The ZEV requirements for each model year are the same in both states, as required by the federal Clean Air Act.

In California, Advanced Clean Trucks took effect with model year 2024, which had a 5-9% ZEV sales/credit requirement. In Washington, Advanced Clean Trucks took effect with model year 2025, which has a 7-11% ZEV sales/credit requirement, matching the 2025 requirement in California.

Manufacturers selling in Washington have been able to generate and bank credits since 2021 without having to use them for compliance until model year 2025 — one more year of early-action credits than California.

Washington’s Transportation Electrification Strategy closely examined Washington’s trucking fleet to determine a feasible path toward electrification. They found that, because of lower fuel costs and maintenance costs, total cost of ownership for a zero-emission truck is or will be lower than for a comparable internal combustion engine truck in many cases.

This financial benefit is expected to grow over time as truck and refueling infrastructure costs decline. For zero-emission vehicles that still have a higher total cost of ownership than their gas or diesel counterparts, zero-emission options are projected to reach cost parity in the early 2030s, depending on vehicle type. The International Council on Clean Transportation released a Total Cost of Ownership Calculator. This calculator compares the lifetime costs of zero-emission battery electric powertrains to diesel commercial vehicles.

To help with the upfront costs, the state has provided funding from the Climate Commitment Act to establish WAZIP (Washington Zero-Emission Incentive Program). WAZIP is a program to help truck owners cover the costs of electric medium- and heavy-duty vehicles and charging infrastructure. WAZIP funds are available as of April 2026.

Additionally, to reduce diesel emissions, we provide grant funding to help fleet managers replace old engines, install exhaust retrofit equipment, reduce idling, and use cleaner fuels.

After successful litigation led by Washington state, National Electric Vehicle Infrastructure (NEVI) Formula Program funds have been unfrozen. The NEVI program is run by the Federal Highway Administration (FHWA) and provides funding for EV chargers. FHWA issued a notice of proposed modification in February 2026 stating that it is considering changing the current Build America Buy America (BABA) requirements for EV chargers that receive federal funding. The domestic-content threshold for charger components would go from 55% up to 100% of total component cost.

Advanced Clean Trucks requirements were created to be achievable even in the absence of public charging infrastructure; they were written with only depot charging in mind. Fleets still have the ability to choose which routes and payloads work best with ZEVs, but the state is continuing to invest in charging infrastructure to support the adoption of medium- and heavy-duty electric and hybrid vehicles. Washington is committed to supporting the trucking industry through the transition to clean vehicles.

$112 million in funding from the Climate Commitment Act is being provided to help truck owners cover the costs of electric medium- and heavy-duty vehicles, as well as depot charging infrastructure. $18 million is being provided to help school districts cover similar costs. Additional state support has been made available through the Clean Fuel Standard, state tax credits on commercial ZEVs and associated infrastructure, as well as Volkswagen Settlement grants, Clean Diesel grants, and the Zero-Emission School Bus grant program.

We’re leveraging federal funding, too. The federal government announced awards under the Charging and Fueling Infrastructure grant program for Washington, Oregon, and California to build an electric truck charging corridor along the entirety of I-5.

To find a charging station on the west coast visit the, EV Mapping and Planning Tool Application. For charging stations around the nation, visit the Plug Share website.

Contact information

Caroline Halter
Communications Manager
Caroline.Halter@ecy.wa.gov
564-669-8947

Clean Vehicles Program team
CleanVehicles@ecy.wa.gov