California: Light-duty: GHG


For cars with the model year of 2017 and beyond, California applies the LEV III standard to reduce GHG emissions. Fleet-wide GHG parameters are established based on vehicle size and decrease at a rate of about 4.9% per year for cars and about 4.5% per year for light trucks through 2025.

Standard type
Greenhouse gas emission limits

The total fleet of passenger and non-passenger vehicles manufactured for sale in the United States, up to a GVWR of 10,000 lbs.


In 2002, California enacted first-of-its-kind legislation regulating greenhouse gas (GHG) emissions from motor vehicles. California Assembly Bill 1493 (Pavley) required “the state board to develop and adopt, by 1 January 2005, regulations that achieve the maximum feasible reduction of greenhouse gases emitted by passenger vehicles and light-duty trucks.”1

In September 2004, CARB approved regulations to control GHG emissions from new LEV II vehicles beginning with the 2009 model year. To the vehicular criteria and toxic air contaminant emissions that California was already regulating, these new GHG regulations added four greenhouse gas air pollutants: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and hydro-fluorocarbons (air conditioner refrigerants, like R-134a).

California has since adopted amendments to the “Pavley” regulations that deem compliance with the federal EPA standards for MY 2012-2016 as sufficient to demonstrate compliance with the California standards. Since then, CARB, EPA, and NHTSA have coordinated to develop fuel economy and GHG standards for model year 2017-2025 standards.

Technical Standards


The GHG standards are incorporated into low emission vehicle (LEV) regulation, and there are two fleet average GHG requirements: (1) for passenger car/light-duty truck 1 (PC/LDT1) category, which includes all passenger cars and light-duty trucks below 3,750 lbs equivalent test weight (ETW); and (2) for light-duty truck 2 (LDT2) category, including light trucks between 3,751 lbs ETW and 8,500 lbs gross vehicle weight (GVW). In addition, medium-duty passenger vehicles (MDPVs) from 8,500 to 10,000 lbs GVW are included in the LDT2 category for GHG emission standards.

The standards phase-in over the period of 2009 to 2016. The average gram-per-mile reduction of GHG emissions from new California cars and light trucks will be about 30% in 2016, compared to model year 2004 vehicles.

The GHG emission standards are defined in grams per mile of CO2-equivalent emissions, calculated from the following formula:

CO2-Equivalent = CO2 + 296 × N2O + 23 × CH4 – AC Allowances
California Fleet Average GHG Emission Standards
Year GHG Standard, g CO2/mi (g CO2/km) CAFE Equivalent, mpg (l/100 km)
2009 323 (201) 439 (274) 27.6 (8.52) 20.3 (11.59)
2010 301 (188) 420 (262) 29.6 (7.95) 21.2 (11.10)
2011 267 (166) 390 (243) 33.3 (7.06) 22.8 (10.32)
2012 233 (145) 361 (225) 38.2 (6.16) 24.7 (9.52)
2013 227 (142) 355 (221) 39.2 (6.00) 25.1 (9.37)
2014 222 (138) 350 (218) 40.1 (5.87) 25.4 (9.26)
2015 213 (133) 341 (213) 41.8 (5.63) 26.1 (9.01)
2016 205 (128) 332 (207) 43.4 (5.42) 26.8 (8.78)

A manufacturer may use N2O = 0.006 g/mi in lieu of measuring N2O exhaust emissions. The AC emission allowances are determined based on the design of the air conditioning system (i.e., with higher allowances for more leak-resistant systems, lower global warming potential refrigerants, and more energy-efficient systems).

The sets of CO2 emissions are based on the vehicle laboratory measurements from the FTP “city” test cycle and the HWFET “highway” test cycle. The city values are taken with a weight factor of 55%, and the highway values with a weight of 45%, before manufacturers calculate the sales-weighted average emission levels from all their vehicles manufactured for sale in California. Additional adjustment factors are used for calculation in vehicles fueled by alternative fuels and zero-emission vehicles (ZEVs) according to their relative lifecycle emissions of electricity or hydrogen use.

The regulation also includes GHG emission credits for manufacturers who have emissions below the standards. Credits can be earned for reductions in GHG emissions achieved in model years 2000-2008 (i.e., prior to the date the regulation became effective) and during the phase-in period. Accumulated credits can be used to offset compliance shortfalls up to one year after the end of the phase-in at full value, or in the second and third years after the end of the phase-in at a discounted rate.


GHG emission limits, as part of LEV III standards, for new 2017 and subsequent model years apply to passenger cars, light-duty trucks, and medium-duty passenger vehicles. Light-duty trucks from 3751 lbs. ETW (equivalent test weight) – 8500 lbs. GVW that are certified to the Option 1 LEV II NOx Standard are exempt from these GHG requirements, however, passenger cars, light-duty trucks 0-3750 lbs. LVW, and medium-duty passenger vehicles are not eligible for this exemption.

Credit Provisions

Emission reduction compliance credits include air-conditioning system technology, flexible fuel vehicle deployment, off-cycle technologies, incentives for electric vehicles, and “game-changing” technologies installed on pickup trucks.

Regulatory design

The California 2017-2025 regulations introduce vehicle size-based standards for the two vehicle categories, following the current federal 2012–2016 standard framework. Separate numerical standards for vehicle size or “footprint” are used for passenger cars and for light trucks. Because there are two categories, car and truck, and the standards are based on the footprint attributes of future year vehicle sales, the exact GHG emission outcome from the program is somewhat unknown and subject to the sales mix of vehicles sold in the future. Each auto manufacturer will ultimately have a different footprint-based standard based on its sales mix of vehicles at each vehicle size and its car and light truck sales mix.


The fleet average CO2 exhaust mass emission target values (indexed by vehicle footprint) for passenger cars, light-duty trucks that are produced and delivered for sale in California would be reduced by about 34% from model year 2016 through 2025. The LEV III GHG rule-making would reduce the CO2 emissions of cars by about 4.9% per year and light trucks by about 4.5% per year from 2016-2025 to achieve a combined emission rate of 166 g CO2/mi.

Projected CO2 emissions by model year from LEV III GHG regulations
Model Year Car Truck Combined light-duty
gCO2/mi Annual change gCO2/mi Annual change gCO2/mi Annual change
Baseline 2008 291 396 336
Previous Rule Targets 2013 256 2.8% 330 2.8% 283 2.6%
2014 248 3.3% 321 2.8% 275 2.8%
2015 236 4.5% 306 4.5% 263 4.3%
2016 226 4.5% 292 4.5% 251 4.4%
Proposed Rulemaking Targets 2017 213 5.5% 290 0.7% 243 3.2%
2018 203 4.9% 280 3.5% 233 4.2%
2019 192 5.2% 273 2.8% 224 4.0%
2020 183 4.9% 264 3.0% 215 3.9%
2021 173 5.5% 245 7.5% 201 6.3%
2022 165 4.4% 233 4.9% 192 4.6%
2023 158 4.5% 221 4.9% 183 4.8%
2024 151 4.5% 210 5.0% 174 4.8%
2025 144 4.6% 200 4.9% 166 4.8%
Average change, (2016-2025) 4.9% 4.1% 4.5%
Change, 2008-2016 -23% -26% -25%
Change, 2016-2025 -36% -32% -34%
Change, 2008-2025 -51% -50% -51%
Notes: Car, truck, overall targets shown are based on projected sales of vehicles by footprint, category (ultimate gCO2/mile levels are determined by end-of-year sales); the original California GHG standards for model years 2009-2011 are based on a different two-category system (PC/LDT1 and LDT2) than the car and truck system of the 2012-2016 federal standards and proposed 2017-2025 standards; Difference of individual columns may not match due to rounding.

Since the adoption of the 2017-2025 California LEV III GHG standards, the substantially similar federal 2017-2025 standards have been adopted, and the state of California has agreed to deem compliance with the federal standards as sufficient for compliance with the LEV III standards.

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