Air Conditioning Credits in the LightDuty GHG Rule (and Beyond)

29 Jan 2011

Update for 2011 MACS 

Convention

Brian Nelson - US EPA
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Key Elements Concerning A/C Credits

 “Leakage” credits are calculated using the method described in 

SAE J2727 (August 2008 version)

 “Efficiency” credits are calculated using menu-based approach, 

where design/control attributes of the vehicle’s A/C system are 

used to determine the amount of the credit:

– For model years 2012 and 2013, only the menu is used

– For model years 2014 through 2016, the menu is supplemented by an A/C Idle 

Test

– The A/C Idle Test is used to measure the incremental CO2 emissions due to 

A/C Use, and adjust the credit amount downward if test result less than 14.9 

g/min.

 “Off-Cycle” credits are those which are not capture in an existing 

test cycle or menu item

– Mfr. must justify rationale for granting an off-cycle credit for “new and 

innovative” technologies

– Standard test metric does not exist for off-cycle credits
A/C Efficiency Credit Adjustment (2014-

2016 only)

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0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

14.0 15.0 16.0 17.0 18.0 19.0 20.0 21.0 22.0

Credit Adjustment Factor

A/C Idle Test Result (g/min.)

If test result is 

14.9 g/min. or 

less, the 

vehicle

receives 100% 

of the

applicable A/C 

efficiency

credit

If test result is 

21.3 g/min. or 

greater, the 

vehicle 

receives 0% of 

the applicable 

A/C efficiency 

credit

If test result is greater than 

14.9 g/min., but less than 

21.3 g/min, the applicable 

A/C efficiency credit is 

adjusted downward, as a 

function of the test result
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What We Finalized in the A/C Credit Menu
Early A/C Credits

 Available in MYs 2009 – 2011

 Credits determined using same methodology as used for 

MY2012 A/C credits

 To earn early A/C credits for vehicles in California and CAA 177 

states, the manufacturer must use one of the EPA early CO2 

credit Pathways that covers those vehicles

 For vehicles outside of California and CAA 177 states, 

manufacturers may earn early A/C credits regardless of 

whether or not the vehicles are included in an early CO2 credit 

Pathway 

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Development of New Test Methods

 Have begun discussions with stakeholders to establish a 

framework for quantifying the power consumed by vehicle A/C 

systems:

– Development of test methods/procedures

– Use of models to determine expected power consumption

– Verification of model results with vehicle-level testing

 What we said in the Final Rule concerning next steps:

– “While EPA considers a test cycle that covers a broader range of vehicle 

speed and climatic conditions to be ideal, developing such a representative 

A/C test would involve the work of many stakeholders, and would require a 

significant amount of time, exceeding the scope of this rule. EPA expects 

to continue working with industry, the California Air Resources Board, and 

other stakeholders to move toward increasingly robust performance tests 

and methods for determining the efficiency of mobile A/C systems and the 

related impact on vehicle CO2 emissions, including a potential adapted 

SC03 test.”
Future Rulemaking Proposals:

 From Heavy-Duty GHG Proposed Rule, Federal Register / Vol. 75, No. 229 / 

Tuesday, November 30, 2010 / Proposed Rules, page 74163:

“In addition to the proposed EPA tractor- and engine-based standards for CO2 

and engine-based standards for N2O, and CH4 emissions, EPA is also 

proposing a separate standard to reduce leakage of HFC refrigerant from cabin 

air conditioning systems from combination tractors, to apply to the tractor 

manufacturer.”

 From Interim Joint Technical Assessment Report: Light-Duty Vehicle 

Greenhouse Gas Emission Standards and Corporate Average Fuel Economy 

Standards for Model Years 2017-2025, September 2010, page D-5:

“Our proposed approach would associate each component with a specific 

leakage rate in grams per year identical to the values in J2727 and then sum 

together the component leakage values to develop the total A/C system 

leakage. However, in this “percent system leakage per year” approach, the total 

A/C leakage score and is then divided the value by the total refrigerant system 

capacity to develop a percent leakage per year.” 7
Questions/Comments?

For more information, contact Brian Nelson 

at the U.S. Environmental Protection Agency:

nelson.brian@epa.gov

734-214-4278 

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