Appendix G 

Technical Support Document 

Staff Analysis on Emissions and Economic Impact of 

Proposed Regulation for Small Containers of 

Automotive Refrigerant 

G-i

Table of Contents 

1. INTRODUCTION.....................................................................................................G-1

2. METHODS ..............................................................................................................G-2

2.1 BAU ................................................................................................................................. G-2 

2.1.1 Practices.................................................................................................................. G-2 

2.1.2 Emissions ................................................................................................................ G-2 

2.1.3 Costs........................................................................................................................ G-3 

2.2 Staff Proposal............................................................................................................... G-4 

2.2.1 Practices.................................................................................................................. G-4 

2.2.2 Emissions ................................................................................................................ G-5 

2.2.3 Costs........................................................................................................................ G-7 

2.2.4 Cost-Effectiveness................................................................................................. G-7 

2.3 Can Ban (Original Proposal in AB 32 Early Action Report 2007) ................... G-7 

2.3.1 Practices.................................................................................................................. G-7 

2.3.2 Emissions ................................................................................................................ G-8 

2.3.3 Costs...................................................................................................................... G-10 

2.3.4 Cost-Effectiveness............................................................................................... G-10 

3. SUMMARY OF RESULTS ....................................................................................G-11

4. DETAILS OF ASSUMPTIONS AND CALCULATION...........................................G-12

4.1 Independent Parameters ......................................................................................... G-12 

4.2 Key Assumptions ...................................................................................................... G-13 

4.3 Analysis........................................................................................................................ G-15 

4.3.1 BAU........................................................................................................................ G-15 

4.3.2 Staff Proposal ....................................................................................................... G-18 

4.3.3 Can Ban................................................................................................................. G-21 

4.4 Detailed Summary of Results................................................................................. G-25 

4.5 Derivation of Key Independent Parameters........................................................ G-26 

4.5.1 Y1 ............................................................................................................................ G-26 

4.5.2 P0 ............................................................................................................................ G-31 

4.5.3 P31, P32, P33, and P34 ............................................................................................ G-32 

4.5.4 F1 and F2................................................................................................................ G-33 

5. REFERENCES......................................................................................................G-35
G-ii

List of Tables 

Table 1: Emissions and Economic Impact of Regulatory Proposals ..........................G-11

Table 2: Independent Parameters .............................................................................G-12

Table 3: Detailed Emissions and Economic Impact of Regulatory Proposals.............G-25

Table 4: Recharge Interval in ARB El Monte Survey .................................................G-27

Table 5: Recharge Interval in 2008 ARPI DIY Survey................................................G-27

Table 6: Storage Period for People Who would Store Partial Cans ...........................G-29

Table 7: Virtual Storage Period for Those Who would Dispose of Partial Cans .........G-30

Table 8: Overall Storage Period ................................................................................G-30

Table 9: NPD Data on HFC-134a Units Sold in the U.S. ...........................................G-31

Table 10: Summary of Recharge Interval Estimates..................................................G-31

List of Figures 

Figure 1. HFC-134a Emissions Associated with DIY Small Can Usage in 2006 ..........G-3

Figure 2. Emissions Impact of Proposed Regulation ...................................................G-6

Figure 3. Detailed Emissions Impact under Proposed Regulation (95% Return Rate).G-6

Figure 4. Detailed Emissions Impact under Can Ban...................................................G-9

Figure 5. DIY Behavior Change under Can Ban........................................................G-33
G-1

Staff Analysis on Emissions and Economic Impact of Proposed 

Regulation for Small Containers of Automotive Refrigerant 

1. INTRODUCTION 

As required by AB 32, the California Air Resources Board (the ARB, the Board) 

has developed a list of early action measures (ARB, 2007a). Six of these early 

action measures are related to Motor Vehicle Air Conditioning (MVAC). 

According to the U.S. EPA Vintaging Model, MVAC systems are the dominant 

user of HFC-134a (Thundiyil, 2005). One of the early action measures, reduction 

of HFC-134a emissions from do-it-yourself (DIY) servicing of MVAC systems, 

has been identified as a Discrete Early Action. DIY servicing involves recharging 

the AC system using small containers (small cans) of refrigerant typically 

containing about 12 ounces of refrigerant in weight, but ranging from 2 ounces to 

2 pounds in weight. The initial proposal contemplated a ban on the sale and use 

of small cans. A small can industry association, Automotive Refrigeration 

Products Association (ARPI), proposed an alternative plan that they claim would 

achieve similar emission reductions at lower cost. Their proposal included selfsealing valve installed on the can, charging a refundable deposit upon sales of 

the cans, and setting up a can return and recycling program. Concerns about a 

ban were also expressed by the AB 32 Environmental Justice Advisory 

Committee (EJAC). The EJAC recommended removing the proposed can ban 

measure from the Early Action list because the committee believed that the 

measure seemed unlikely to achieve the goal of detection and repair of leaking 

auto air conditioning systems, and because it would place a large burden on lowincome people (EJAC, 2007). 

ARB staff explored the impact of adding firm recycling rate targets and a DIY 

education program to the industry proposal, and is proposing this approach as 

the Discrete Early Action. This document compares emission reductions and 

costs associated with the staff proposal and the alternative proposal of can ban. 

The reductions in emissions are calculated in terms of changes from businessas-usual (BAU). The following discussions will first provide an overview of the 

method to calculate emissions and costs, key data, key assumptions, and results. 

It will be followed by the details of the assumptions and calculation. 
G-2

2. METHODS 

2.1 Business-as-usual (BAU) 

2.1.1 Practices 

DIY practice involves puncturing a one-way can of refrigerant with a low cost 

apparatus consisting of a valve and hose, connecting the apparatus to the low 

pressure (suction) side of the AC system, and transferring refrigerant from one or 

more small cans to the AC system over the course of many minutes. There are 

two immediate sources of emissions resulting from this process. First, some 

refrigerant escapes from the can and apparatus during the servicing process, 

which is called servicing losses. Second, some of the refrigerant typically 

remains in the small can after the refilling process has been completed. This 

remainder is called the can heel. Because most cans do not include a means to 

close themselves, the entire can heel is emitted to the atmosphere shortly after 

the can is disconnected from the recharge apparatus. 

In addition to the immediate emissions there are also delayed emissions that can 

be associated with DIY practice. The AC system that receives charge from the 

DIY small can has leaked, hence the need for recharge. Not all DIY service 

operations are necessarily on systems that leak more than properly functioning 

systems, but some DIY operators recharge their systems every few months. The 

information needed to determine the distribution of leak rates from DIY vehicles 

is not readily available. But because in most instances the DIY operator is not 

repairing the AC system, but simply re-filling the leaking system, the leak rate is 

very likely to be higher than properly repaired systems. The U.S. EPA Vintaging 

Model assumes that a properly functioning system should only need to be 

recharged after about 6 years (Thundiyil, 2008a). The difference in leak rates 

between DIY serviced and professionally serviced systems is an emission that 

can be attributed to DIY practice. Professional service technicians are required to 

fully diagnose the AC system before repairing or recharging it. A large fraction of 

customers choose to make repairs, even though some choose to simply 

recharge or top off, and some choose to reject repairs and forgo air conditioning 

(see 4.5.3). 

2.1.2 Emissions 

ARB’s Survey of Consumer Products for 2006 estimates that California sales of 

HFC-134a in small containers are 654 metric tons in about 2 million cans (ARB, 

2007b). Using a global warming potential (GWP) of 1300 for HFC-134a (IPCC, 

2007), the annual sales correspond to 0.85 million metric ton CO2 equivalent 

(MMTCO2E) per year. Based on information from a MVAC trade association 

(Atkinson, 2008a; MACS, 2008), it is estimated that only 5% of small cans sales, 

or 0.04 MMTCO2E per year of HFC-134a, are made to automotive repair shops, 

suggesting that 95%, or 0.81 MMTCO2E per year of HFC-134a are used by DIY. 
G-3

This analysis only considers small can operations performed by individual 

consumers as DIY emissions. We do not include emissions associated with small 

can use by professionals, nor do we include reductions of these emissions by the 

proposed mitigation measures. 

The fraction of DIY can use apportioned to servicing losses, can heels, and 

system charge is estimated to be 11%, 22%, and 67%, respectively. These 

figures are based on research commissioned by ARB (Clodic et al., 2008). The 

immediate emissions are thus approximately 0.23 MMTCO2E per year and the 

delayed emissions are approximately 0.48 MMTCO2E per year. The following 

figure illustrates the emissions associated with DIY practice. 

Figure 1. HFC-134a Emissions Associated with DIY Small Can Usage in 

2006

In order to project BAU into the future, several major factors are analyzed. First, 

the increase of passenger vehicle population and better refrigerant containment 

would likely keep the number of leaky vehicles unchanged. Second, the 

decrease in AC nominal charge size and better refrigerant containment may keep 

the recharge frequency unchanged. Furthermore, the amount of refrigerant 

consumed per recharge will not change due to the characteristics of DIY 

recharging. Therefore, the annual emissions from DIY recharging of MVAC are 

projected to remain roughly constant (at 0.81 MMTCO2E per year) through 2020 

under BAU. A detailed analysis is presented in 4.3.1. 

2.1.3 Costs 

The annual consumer costs associated with BAU are estimated based on the 

average retail cost per can. Based on the NPD Automotive Aftermarket Industry 

Monitor Data from the total U.S. auto parts chain retailers sales records (NPD, 

HFC-134a Sold in Small 

Cans in CA Currently: 

0.85 MMTCO2E/yr. 

Sold to DIYers: 

95% 

0.81 MMTCO2E/yr. 

Sold to Professional Shops:

5% 

0.04 MMTCO2E/yr. 

Effective Charge: 

67% 

0.54 MMTCO2E/yr. 

Servicing Loss: 

11% 

0.09 MMTCO2E/yr. 

Can Heel: 

22% 

0.18 MMTCO2E/yr.

Immediate Emissions Delayed Emissions
G-4

2008), the cost average out to about $13 per can, including the cost of the 

transfer apparatus. 

To estimate lifetime costs and costs per consumer, it is necessary to estimate 

vehicle life and the rate at which the vehicle needs service. Based on a study 

carried out by ARB staff in support of the AB 1493 regulation development 

(Vincent et al., 2004), the average vehicle lifetime in California is 16 years. Based 

on the I-MAC study (I-MAC Team, 2007), the average time for which a new 

vehicle will not need AC service is about 7 years. This is also consistent with 

ARB’s study (Vincent et al., 2004). The estimated portion of time for which an 

average vehicle needs servicing is then 9 years. For vehicles receiving DIY 

servicing, it is assumed that the leaks are not repaired, and it is estimated that 

the vehicle is recharged about once per year, primarily during summer, based on 

various data sources. This generates 9 DIY servicing over the 9 years of service 

need. 

To estimate costs per consumer, it is necessary to estimate the number of 

vehicles needing service. The ARB study data indicates that the average number 

of cans used per service is 1.3 (Clodic et al., 2008). Given that 1.8 million cans 

per year are used by DIY operators, about 1.4 million DIY service operations 

occur each year. Given a DIY service rate of once per year per vehicle, the total 

number of vehicles that have ever been DIY serviced in the whole in-use fleet is 

1.4 million. They are referred to as “DIY vehicles” hereafter in this document. It 

should be noted that these vehicles have a spectrum of leakage rate. Some of 

them function normally and only need recharge every several years. Some of 

them have leaking problem and need frequent recharge, likely more than once 

per year. So the number of vehicles that actually get recharged in any year 

should be significantly less than 1.4 million. At 1.3 cans per service and about 

$13 per can, the average costs of one DIY service are about $17. The costs per 

vehicle per year are then about $17. The annual costs to consumers for 1.8 

million cans at about $13 each are about $24 million per year. The costs of 9 DIY 

service operations over the life of the vehicle are about $152. 

2.2 Staff Proposal 

2.2.1 Practices 

ARB staff is now proposing a comprehensive approach as the Discrete Early 

Action measure to reduce emissions associated with DIY servicing of MVAC 

using small cans. The emission reductions would be achieved through the use of 

a self-sealing valve on the can, improved labeling instructions, a recycling 

program for used cans, and an education program that emphasizes best practice 

techniques for vehicle recharging as well as highlights the environmental risks 

associated with this product. A mandatory return rate target will be set at 90% for 

the first two years of the regulation, and 95% for the following years. As an 

incentive to promote return of the cans, a deposit of $10 (approximately 
G-5

equivalent to the price of a 12-ounce can) will be collected at time of the sales 

and will be refunded when the consumer returns the cans. If the return rate target 

is not met by the end of the first two years, the deposit will be increased by $5. 

This process would continue until the target recycle rate is achieved. 

Improved usage instructions on the small cans and DIY education program will 

better inform consumers of the potential risk to their AC and damage to the 

climate system from DIY recharging, thus discourage some of them continuing 

DIY recharging. However, this cannot be quantified at this point. In this analysis, 

it is assumed that no consumer would change DIY behavior due to this regulation. 

2.2.2 Emissions 

We expect that the consumer education program would increase the number of 

DIY users motivated to find and repair leaks. However, no data are available to 

quantify this change in consumer behavior. For purpose of analysis the delayed 

emissions of 0.54 MMTCO2E per year are assumed to remain the same and will 

be addressed through other regulatory approaches, such as improving 

professional servicing and identifying and repairing leaky MVAC systems via the 

smog check program. 

The emissions due to can heels were 0.18 MMTCO2E per year under BAU. With 

the self-sealing valve, the heel will be contained in the can. If the target return 

rate of 90% is met for the first two years, these emissions will be reduced to 0.02 

MMTCO2E per year. If the 95% return rate target is met for the years to follow, 

the can heel emissions will be reduced to 0.01 MMTCO2E per year. 

It is anticipated that with self-sealing valve, improved can instructions, and DIY 

education program, the servicing losses would be reduced to minimal. Thus, the 

0.09 MMTCO2E of annual emissions due to servicing are eliminated. 

Therefore, the annual emissions under this proposal would be 0.56 MMTCO2E 

for the first two years, achieving annual emission reductions of 0.25 MMTCO2E. 

For the following years, the emissions would be 0.55 MMTCO2E per year and 

emission reductions are thus 0.26 MMTCO2E per year (Figure 2). Figure 3 

illustrates the detailed breakdown of the emissions impacts of the proposed 

regulation when the final return rate target of 95% is reached. 
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Figure 2. Emissions Impact of Proposed Regulation 

Figure 3. Detailed Emissions Impact under Proposed Regulation 

(95% Return Rate) 

Servicing Loss: 

11% 

0.09 MMTCO2E/yr. 

Effective Charge: 

67% 

0.54 MMTCO2E/yr. 

Total Emissions under BAU: 

0.81 MMTCO2E/yr. 

0.17 MMTCO2E/yr. 

Eliminated 

Returned: 

95% 

0.54 MMTCO2E/yr. 

Remaining the Same 

0.01 MMTCO2E/yr. 

Remaining the Same 

Unreturned: 

5% 

Can Heel: 

22% 

0.18 MMTCO2E/yr. 

0.09 MMTCO2E/yr. 

Eliminated 

Total Emissions under Staff Proposal: 

0.55 MMTCO2E/yr. 

Total Emission Reductions: 

0.26 MMTCO2E/yr.

2006 2010 2012 2020 

Annual Emissions (MMTCO2E)

0.81 

0.56 

0.55 

BAU 

90% Return Rate 95% Return Rate

Year

Proposed Regulation 

Emission Reductions
G-7

2.2.3 Costs 

The extra cost of $1 per can due to the self-sealing valve and recycling program 

would be passed on to the consumer in the increased price of the can. At 1.8 

million cans per year the increased consumer costs are $1.8 million. The extra 

costs include about $0.25 per can for the valve, and about $0.75 per can to cover 

the costs of return shipping for the cans, extracting and recycling the can 

contents, and reporting to ARB. 

Given a 95% can return rate and a $10 deposit per can, the 5% of unclaimed 

deposits come to $0.9 million per year and will be additional costs to the 

consumers. 

Total increased costs to the consumer are thus $2.7 million per year. 

2.2.4 Cost-Effectiveness 

Under this proposal, about 0.26 MMTCO2E of emissions would be reduced per 

year at an increased cost of $2.7 million per year. The cost-effectiveness is then 

about $11/MTCO2E. 

2.3 Can Ban (Original Proposal in AB 32 Early Action Report 2007) 

2.3.1 Practices 

The can ban remains as an alternative proposal. Ideally, there would no longer 

be any DIY servicing if a can ban is in place. All servicing would be done by 

professional shops. Some consumers would forgo air conditioning and some 

would take their vehicle to the professional shops. In practice, some DIY will 

evade the regulations and acquire HFC-134a for DIY operations. Professional 

shops in California are required by the California Bureau of Automotive Repair 

(BAR) to conduct complete diagnostics prior to recharging an auto AC system. 

Based on trade association survey data a large fraction of vehicles brought to a 

professional shop are repaired before being released in a recharged state. The 

repairs conducted by professional shops are expected to last 6 years (Thundiyil, 

2008a), thus reducing the emission rate for former DIY vehicles to one sixth of its 

pre-repair value. During professional repair and recharge, a certain amount of 

refrigerant will be emitted due to servicing losses and cylinder heel emissions. 

There will also be some professionally serviced vehicles that may need repairs 

but receive a recharge only or a top off. There will also be professional serviced 

vehicles for which repairs are not effective. For purpose of analysis these 

vehicles are considered part of the group of vehicles that receive a professional 

recharge service or top off without repair. 
G-8

2.3.2 Emissions 

Under the ban, the treatment of the delayed emissions of 0.54 MMTCO2E per 

year from leaking vehicles is divided into categories based on consumer choices. 

The emission reductions are different for each category. Based on an ARPI 

commissioned survey (Frost and Sullivan, 2006), A MACS survey (Atkinson, 

2008b), and an IMR survey (ARPI, 2008a), it is estimated that 32% of the original 

DIY consumers would pay for professional repair and recharge, 23% of them 

would have professional technicians recharge their AC without repair, 7% would 

choose topping off at professional servicing, 19% would continue DIY recharging 

using small cans obtained from alternative ways, and the remaining 19% would 

forgo AC.

The 32% of vehicles that receive professional repair are assumed to have their 

original recharge frequency of once per year reduced to once charge per 6 years. 

On the other hand, it is estimated that every professional recharge uses 1.6 

times as much as the fresh refrigerant used in DIY recharge. Therefore, the 

delayed emissions of 0.17 MMTCO2E per year become 0.27 MMTCO2E per 6 

years, or 0.045 MMTCO2E per year. A U.S. EPA testing study on the heel from 

disposable containers (U.S. EPA, 2007) suggests the average cylinder heels are 

about 2%. So the heel emissions are about 0.001 MMTCO2E per year. It is 

assumed there is no fresh refrigerant lost in the form of servicing losses during 

professional recharging. 

The 23% of vehicles that receive professional recharge without repair would then 

leak at their pre-servicing rate. Nonetheless, the professional technicians have 

the equipment and skills to charge AC to their nominal charge. The next recharge 

will not take place until the AC loses 50% of the nominal charge again. In 

contrast, DIY on average undercharge their AC. It is estimated that a 

professionally recharged AC has 1.4 times as much refrigerant to lose as that of 

a DIY recharged AC. Therefore, a professionally recharged AC has longer 

interval between two recharges, 1.4 times as long as that of a DIY recharged AC. 

On the other hand, the average professional recharge uses 1.6 times as much as 

the refrigerant used by DIY. Therefore, the delayed emissions of 0.12 MMTCO2E 

per year are changed to 0.2 MMTCO2E per 1.4 years, or 0.14 MMTCO2E per 

year. The heel emissions work out to be about 0.003 MMTCO2E per year. No 

fresh refrigerant will be lost as servicing losses.

The 7% of vehicles that are topped off at professional servicing will emit at their 

original rate. Therefore, the delayed emissions of 0.04 MMTCO2E per year 

emitted by these vehicles remain the same. In addition, topping off would incur 

0.013 MMTCO2E per year in heel emissions and 0.006 MMTCO2E per year in 

servicing losses. 

The 19% that remain DIY recharging using small cans obtained from alternative 

ways will also emit at their original rate. Therefore, the delayed emissions of 0.1 
G-9

MMTCO2E per year emitted by these vehicles remain the same. Another 0.033 

MMTCO2E per year in heel emissions and 0.016 MMTCO2E per year in servicing 

losses would occur. 

The rest 19% of vehicles would forgo AC, thus no longer emit refrigerant. 

Therefore 0.1 MMTCO2E of delayed emissions per year are reduced to zero. 

Apparently, there are no immediate emissions associated with this group of 

vehicles. Forgoing MVAC has potential consequences for indirect emissions 

because consumers without AC would likely drive with windows rolled down for a 

large share of vehicle-miles-traveled (VMT). The increased load due to increased 

drag force must be balanced against the reduced load due to non-operation of 

the AC compressor. At high speed, indirect emissions might be increased. At low 

speed, indirect emissions will be reduced. On average, the change in indirect 

emissions due to non-operation of the MVAC is expected to be a net reduction 

(i.e., forgoing AC would probably reduce indirect emissions). Changes in indirect 

emissions have not been included in this analysis. 

The total annual emissions under can ban are thus 0.4 MMTCO2E. The annual 

emission reductions are 0.41 MMTCO2E. Figure 4 shows the emissions impact of 

the can ban approach. 

Figure 4. Detailed Emissions Impact under Can Ban 

Total Emission Reductions: 

0.41 MMTCO2E/yr.

Total Emissions under BAU:

0.81 MMTCO2E/yr. 

Servicing Loss: 

11% 

0.09 MMTCO2E/yr.

Effective Charge: 

67% 

0.54 MMTCO2E/yr. 

Can Heel: 

22% 

0.18 MMTCO2E/yr.

Pro. Repair/Recharge:

32% 

Pro. Recharge only: 

23% 

Forgo AC: 

19% 

Pro. Top off: 

7% 

Obtain Refrigerant 

from Other Means: 

19% 

0.17 MMTCO2E/yr. 

Become 

0.045 MMTCO2E/yr.

0.12 MMTCO2E/yr. 

Become 

0.14 MMTCO2E/yr. 

0.1 MMTCO2E/yr.

Eliminated 

0.04 MMTCO2E/yr.

Remain the Same 

0.1 MMTCO2E/yr. 

Remain the Same 

Effective Charge: 

0.14 MMTCO2E/yr. 

Immediate Emissions:

0.07 MMTCO2E/yr. 

Effective Charge: 

0.185 MMTCO2E/yr.

Immediate Emissions:

0.004 MMTCO2E/yr.

Total Emissions under Can Ban: 

0.40 MMTCO2E/yr. 
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2.3.3 Costs 

Under the can ban, consumer costs would be affected mainly by the difference 

between the cost of professional repairs and the cost of DIY recharges. DIY 

recharges were estimated to occur at a rate of once per year, at cost of about 

$17 per year. Professional diagnosis/repairs/recharges are estimated to cost 

about $650. This is based on the 2003 MACS Survey which shows that a 

professional repair costs $508 on average in 2003 (MACS, 2008), which is about 

$580 in 2007 dollars. We then add a $70 recharge charge on top of that. 

Professional repair/recharge is assumed to occur every 6 years on average for a 

cost of $108 per year for the 32% of consumers choosing professional repair. 

Professional recharge without repair is estimated to cost about $100 (Clodic et al., 

2008) and is assumed to occur every 1.4 years for a cost of $71 per year for the 

23% of consumers choosing professional recharge. Professional topping off is 

estimated to cost about the same as professional recharge, $100 (Clodic et al., 

2008), and to occur once a year on average for a cost of $100 per year for the 

7% of consumers choosing to have their system topped off. About 19% of 

consumers would still DIY recharge their vehicles once a year using refrigerant 

that they obtain from alternative ways, at a cost assumed to be 50% higher than 

under BAU, or about $25 per year. For the approximately 1.4 million vehicles 

involved, the total consumer costs increase from $24 million to $88 million, an 

increase of $65 million annually. For individual owners, the vehicle lifetime costs 

increase from $152 for 9 DIY recharges to $975 for 1.5 professional repair and 

recharge services, to $643 for 6.4 professional recharges, to $900 for 9 top offs 

at professional servicing, or to $228 for 9 DIY recharges using HFC-134a 

obtained by alternative means. In addition, about 19% of consumers do not pay 

the increased cost, and therefore have no air conditioning in their vehicles. 

There would be no costs or charges imposed on the small can industry to comply 

with the ban, but there would be complete loss of revenue from the small can 

business in California. Annual can sales to DIY owners are about 1.8 million at 

an average retail price of about $13 including cost of transfer apparatus. The 0.1 

million cans sold to professional AC shops are also assumed to be at $13 per 

can for purpose of analysis. Therefore, industry would lose annual revenues of 

about $25 million due to the can ban. 

Under the can ban, the professional MVAC repair industry would see a revenue 

increase equal to the amount paid by former DIY operators to obtain professional 

repairs. This amount is estimated to be $82 million per year. 

2.3.4 Cost-Effectiveness 

The emissions reduction under the can ban is 0.41 MMTCO2E per year. The 

increase in consumer costs is $65 million per year. The cost per metric ton of 

reduction borne by the consumer is then about $159/MTCO2E. 
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3. SUMMARY OF RESULTS 

DIY recharging of MVAC systems with HFC-134a generates emissions of about 

0.81 MMTCO2E per year. 

ARB staff proposes a comprehensive measure that could achieve emission 

reductions of 0.26 MMTCO2E per year even if no DIY consumers change their 

behavior. The cost-effectiveness works out to be $11/MTCO2E and industry 

would likely see no revenue losses. 

The alternative can ban approach would eliminate approximately 0.41 MMTCO2E 

per year of HFC-134a emissions from DIY recharging of MVAC using small cans 

at a cost of about $159/MTCO2E to the consumer plus $25 million per year in lost

revenues to industry. 

Table 1: Emissions and Economic Impact of Regulatory Proposals 

Scenario 

Emissions 

MMTCO2E/yr.

Emission 

Reductions 

MMTCO2E/yr.

CostEffectiveness 

Dollars/MTCO2E

Lost Revenue 

Million Dollars/yr. 

BAU 0.81 NA NA NA 

Staff Proposal* 0.55 0.26 11 0 

Can Ban 0.4 0.41 159 25 

* Calculation based on a can return rate target of 95%. 

 
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4. DETAILS OF ASSUMPTIONS AND CALCULATION 

4.1 Independent Parameters 

Table 2: Independent Parameters 

Notation Definition Estimate References 

Stot Number of small cans sold annually in CA 2 million ARB, 2007b 

Etot

Amount of HFC-134a sold in small cans 

annually in CA 

0.85 

MMTCO2E Same as the above 

Y Vehicle’s average lifetime 16 years Vincent et al., 2004 

Y0

Average time after which a leaky vehicle’s AC 

needs its first recharge 7 years I-MAC Team, 2007 

Y1

Average time that a leaky MVAC recharged 

without repair lasts before it needs another 

recharge 

1 year ARB staff estimate (see 4.5.1) 

Y2

Average time that a leaky MVAC repaired and 

recharged by a professional shop lasts before it 

needs another repair and recharge 

6 years Thundiyil, 2008a 

NC

Average number of small cans needed for a 

DIY recharging event 1.3 cans Clodic et al., 2008 

P0

Percentage of HFC-134a in small cans sold to 

DIY in CA 95% ARB staff estimate (see 4.5.2) 

P11

Average percentage of can heels during DIY 

recharging 22% Clodic et al., 2008 

P12

Average percentage of servicing leaks during 

DIY recharging 11% Same as the above 

P2

Percentage of DIY that return the used cans 

(under hybrid approach) 90%, 95% 

Targeted return rates in the 

mandatory small can return / 

recycling program 

P31

Percentage of original DIY (under BAU) that 

would pay for professional diagnosis, repair and 

recharge in case of a can ban 

32% ARB staff estimate (see 4.5.3) 

P32

Percentage of original DIY (under BAU) that 

would choose to evacuate and recharge at 

professional shops in case of a can ban 

23% Same as the above 

P33

Percentage of original DIY (under BAU) that 

would choose to top off with small cans at 

professional shops in case of a can ban 

7% Same as the above 

P34

Percentage of original DIY (under BAU) that 

would choose to continue DIY recharging AC 

using small cans obtained through alternative 

ways in case of a can ban 

19% Same as the above 

P35

Average percentage of fresh refrigerant lost due 

to can heels during professional recharge (in 

relation with total fresh refrigerant usage) 

2% U.S. EPA, 2007 

P36

Average percentage of fresh refrigerant lost due 

to servicing losses during professional recharge 

(in relation with total fresh refrigerant usage) 

0% Most conservative scenario 

based on Clodic et al., 2008 
G-13

P37

Percentage of increase in DIY cost for people 

seeking alternative ways to obtain small cans in 

case of a can ban 

50% ARB staff estimate 

R1 Average retail price for a small can $13 NPD, 2008 

R21

Price increment for a small can under staff 

proposal $1 ARPI, 2008b 

R22

Deposit for a small can under staff proposal $10 Specified value to ensure high 

incentive for return of cans 

R31

Average price for a professional diagnosis, 

repair and recharge of a leaky MVAC $650 

ARB staff estimate based on 

2003 MACS Survey (MACS, 

2008) 

R32

Average price for a professional recharge of a 

leaky MVAC $100 Clodic et al., 2008 

F1

Ratio of effective charge to be leaked out 

before next servicing from professionally 

recharged MVAC to that from DIY recharged 

MVAC 

1.4 ARB staff estimate (see 4.5.4) 

F2

Ratio of effective charge during professional 

recharging to that during DIY recharging 1.6 Same as the above 

4.2 Key Assumptions 

1. The refrigerant charged into a MVAC during the last recharge in its useful 

lifetime is emitted in the same way and amount as the previous recharges. I.e. 

the effect of end-of-life emissions is not taken into account. 

2. The owner of a DIY vehicle maintains his / her repair / recharge preferences 

unless there are regulatory changes. This may not always be the case in reality. 

For example, a consumer could DIY recharge the MVAC this year but have 

professional repair it the next year. Another example is when vehicle ownership 

changes, the new owner may make different decisions on the maintenance of the 

vehicle. But that would make the situation too complicated for the analysis to be 

feasible. 

3. Each DIY consumer (household) owns one and only one DIY vehicle. 

4. MVAC is used throughout a vehicle’s lifetime. 

5. A MVAC has to lose 50% of its refrigerant before a recharge takes place. This 

is based on findings from an ARB sponsored study (Clodic et al., 2008) and is 

consistent with an assumption made in the U.S. EPA Vintaging Model. 

6. Under the staff proposal, no DIY consumer would change his behavior 

(switching to professional servicing, etc.). This is because the increased financial 

burden is mild as long as a consumer returns the used cans for a refund of the 

deposit. The potential risk of DIY recharging MVAC conveyed by the education 
G-14

materials might discourage some consumers to continue DIY recharging. 

However, this effect cannot be quantified at this point. 

7. Under the staff proposal, the effective charge is the same as under BAU. 

Having self-sealing valve and improved usage instructions would likely change 

the percentage. But no data are available to quantify this effect. 

8. Under the staff proposal, servicing leaks can be reduced down to minimal due 

to better usage instructions to the DIY and having self-sealing valves on the can. 

9. Under the staff proposal, the heel in the returned cans would be completely 

recovered, thus causing no emissions. 

10. Under the staff proposal, unreturned cans would end up being disposed of 

and the heel would be emitted to the atmosphere eventually. 

11. Under the staff proposal, the can heel percentage is the same as under BAU. 

Having self-sealing valve and improved usage instructions would likely change 

the percentage. But no data are available to quantify this effect. 

12. The DIY education components of the staff proposal incur no additional costs 

to the consumers. In reality, having the education components might add some 

costs to the industry, which would probably pass the costs on to consumers. 

However, this cannot be quantified. 

13. On average, DIY recharging under the staff proposal uses the same number 

of cans per recharge as under BAU. Having self-sealing valve and improved 

usage instructions would likely reduce the number of cans used per recharge. 

However, no data are available to quantify this effect. 

14. In case of can ban, the behavior changes (switching to professional servicing, 

etc.) of the original DIY consumers are independent of the working conditions of 

the MVAC. The implication is that every new group of vehicles formed by the 

behavior changes of their owners will have the same average leak rate. 

15. Topping off of a MVAC by a professional technician resembles DIY 

recharging at all aspects. It is reasonable to speculate that professional topping 

off using small cans or cylinder and manifold produces less immediate emissions 

and more effectively charges refrigerant into AC than DIY operation. However, no 

data are available to justify it. 

16. In case of can ban, the revenue lost by the small can industry cannot be 

offset by the potential internet or out-of-state sales. Although part of the sales 

may generate revenue to the industry, the sales may depend on a lot of factors 

which are difficult to quantify. 
G-15

4.3 Analysis 

4.3.1 BAU 

According to the ARB Consumer Products Survey for 2006 (ARB, 2007b), the 

small cans of HFC-134a sold in California in 2006 amounted to 

2 million cans Stot = , and Etot = 85.0 MMTCO2E . 

It is estimated (see 4.5.2) that P0 = 95% of the cans are sold to DIY and the rest 

to professional servicing for topping off purposes. Thus, cans used by DIY 

constitute 

95% 85.0 .0 808 (MMTCO E) 2

BAU 0 tot

= × =

E = P ⋅ E

. (4.3.1) 

Per Assumption 1, this equals the annual emissions caused by DIY recharging. 

For purpose of analysis, we convert the emissions to the nominal number of cans 

by assuming 12 oz / can: 

.2 261 10 .0 808 .1 826 (million cans)

.2 261 10

MMT

MMTCO E

1300

kg

MMT 10

oz

kg 12oz .0 02835

6

BAU

6

9 2

BAU

BAU

= × × =

= × ⋅

× × ×

=

−

E

E

S

. (4.3.2) 

This number is used hereafter wherever the number of cans sold to DIY is 

needed. 

The number of unique DIY vehicles is 

.1 404 (million vehicles)

3.1

1 .1 826

C

1 BAU

V

=

×

=

⋅

=

N

Y S

N

, (4.3.3) 

where Y1 is the interval between two consecutive recharges, and NC is the 

number of cans used in each recharge. Note that a vehicle that gets multiple 

recharges during its lifetime is counted as one unique DIY vehicle. According to 

Assumption 2, these vehicles will be DIY recharged during their lifetime unless a 

regulation such as can ban takes effect. Based on Assumption 3, this is also the 

number of unique DIY consumers (households). It is worth noted that quite often 

a vehicle changes ownership. So the group of DIY vehicle owners changes over 

time. 
G-16

It is assumed a MVAC does not need recharging until after Y0 = 7 years in its 

lifetime. So the adjusted lifetime (referred to hereafter as ‘lifetime’) during which 

recharging happens is 

16 7 9 (years)

adj 0

= − =

Y = Y − Y

, (4.3.4) 

where Y = 16 years is vehicle’s lifetime and also the lifetime of MVAC 

(Assumption 4) in California. 

The number of recharges in a DIY vehicle’s lifetime is 

9 (times)

1

9

1

adj

R,BAU

= =

=

Y

Y

N

. (4.3.5) 

The emissions under BAU can also be expressed by a bottom-up approach. 

Under BAU, a DIY recharges the AC when its refrigerant level drops to 50% of 

the nominal charge (Assumption 5). Define MDIY (in MMTCO2E) as the amount of 

refrigerant effectively charged into AC. This equals the amount of refrigerant that 

the AC needs to lose before another recharge becomes necessary. Then over Y1

years the AC leaks until its charge drops to 50% again. Thus each year the AC 

leaks by the amount of MDIY/Y1. However, these gradual leaks (delayed 

emissions) are not the only source of emissions caused by DIY. Losses during 

servicing and due to can heels also need to be taken into account. Thus the total 

annual emissions are 

11 12

1

DIY

V

BAU 1 P P

Y

M

N

E

− −

⋅

= , (4.3.6) 

where P11 and P12 are the fractions of refrigerant lost due to can heel and during 

servicing, respectively, during DIY recharging. 

The annual costs for a DIY vehicle are 

16 90. (dollars)

1

3.1 13

1

C 1

BAU

=

×

=

⋅

=

Y

N R

C

, (4.3.7) 

where R1 is the retail price of a can of HFC-134a. 
G-17

Therefore the annual costs for all DIY vehicles are

.1 826 13 23 73. (million dollars)

all,BAU V BAU BAU 1

= × =

C = N ⋅C = S ⋅ R

. (4.3.8) 

The lifetime costs for a DIY vehicle are 

9 16 90. 152 10. (dollars)

L,BAU adj BAU

= × =

C = Y ⋅C

. (4.3.9) 

In order to project BAU into the future, several major factors need to be taken 

into account. First, the increase of passenger vehicle population and better 

refrigerant containment in newer MVAC will keep the number of leaky vehicles 

unchanged. The EMFAC Model 2007 estimates that the population of passenger 

vehicles in California will increase by around 400,000 each year through 2020. 

But newer MVAC systems have improved designs and improved production 

controls so that they are tighter and have reduced probability of becoming leaky. 

The latter cannot be quantified at this point. So a conservative assumption is 

made that the increased population and decreased probability produces a steady 

multiplication, i.e. the number of leaky MVAC. 

Second, the decrease in MVAC nominal charge size and improvement of 

refrigerant containment will keep the recharge frequency unchanged. The 

average nominal charge size for a new single evaporator MVAC decreases from 

26.9 oz in 2000 to 22.3 oz in 2006 (Atkinson, 2008b). The trend will likely 

continue, but with reduced pace over years. On the other hand, the improved 

refrigerant containment will reduce the leak rate of a leaky AC. In the absence of 

data to quantify the containment improvement, it is reasonable to assume that 

these two factors cancel out the effects from each other, making the recharge 

frequency unchanged. This is consistent with the approach used in the GREENMAC-LCCP Model, which does not differentiate recharge frequency for different 

model year vehicles (Papasavva et al., 2008). As a side note, in the 

development of AB 1493 regulation, ARB staff estimated that California’s MVAC 

emits 55 grams per year on average (ARB, 2004). The MVAC refrigerant 

emissions testing studies conducted by the European Automobile Manufacturers 

Association (ACEA) and Japan Automobile Manufacturers Association (JAMA) 

suggest that newer vehicles leak around 10 grams per year and very few 

vehicles emit significantly more than that (Atkinson, 2008c; Clodic, 2006). This 

substantial difference in leak rate may be attributed mainly to improved 

refrigerant containment of newer AC models as well as deterioration of 

containment over time. 

Lastly, the amount of refrigerant consumed per recharge will not change due to 

the characteristics of DIY recharging. A DIY has no means to know the 

remaining refrigerant level in an MVAC or to determine the proper amount of 

refrigerant to be charged. A DIY terminates charging based on empirical or 
G-18

arbitrary criteria, such as the outflow air temperature, depletion of a can, and 

pressure gauge reading falling into a range specified in charging kit instructions. 

None of these criteria presents solid ground for charging the proper amount of 

refrigerant (Clodic et al., 2008). DIY on average undercharge the current MVAC 

systems. With AC nominal charge decreased, DIY may charge close to the 

correct amount or overcharge. But the number of small cans used per recharge 

is not dependent on the nominal charge size. 

Therefore, the BAU emissions from DIY recharging are projected to remain 

roughly constant at 0.81 MMTCO2E per year through 2020. ARPI had projected 

a 1-2% annual sales growth under BAU, likely based on national sales trend 

(ARPI, 2006). It may not reflect with precision California’s unique usage patterns 

and the various trends discussed above. The uncertainties carried with the 

assumptions in the staff analysis to support this document may overshadow a 1-

2% annual change. Therefore, no attempt has been made to empirically adjust 

the BAU trend to match ARPI’s projection. 

Note that this BAU projection does not account for the potential climate impact 

from other Early Action measures, such as “Addition of AC leak test and repair 

requirement to smog check”, “Requirement of low-GWP refrigerants for new 

MVAC”, and “Reductions of HFC-134a emissions from professional servicing of 

MVAC”. 

4.3.2 Staff Proposal 

ARB staff now proposes a comprehensive approach to reducing the emissions 

from DIY recharging of MVAC. This approach incorporates some of the key 

elements that were proposed by the small can industry association, ARPI, and 

also reflects staff’s modifications. 

Per Assumption 6, all the original DIY consumers would continue DIY recharging 

their MVAC. They would charge the same amount of refrigerant as under BAU 

(Assumption 7). Based on Assumption 8, there are no servicing losses due to 

improved usage instructions and effects of self-sealing valves. Because of the 

mandatory return requirement for the cans and the deposit / refund mechanism, 

most of the DIY consumers (P3) are anticipated to return the used cans, thus 

causing no emissions from can heels (Assumption 9). Those who do not return 

the can will incur heel emissions (Assumption 10) at the same percentage as 

under BAU (Assumption 11). Since the effective charge and leak rate are the

same as under BAU, the recharging frequency is still once every Y1 years. The 

annual emissions are then 

11

1

DIY

2 V

1

DIY

prop 2 V

1

1( )

P

Y

M

P N

Y

M

E P N

−

− ⋅ ⋅

= ⋅ ⋅ + . (4.3.10) 
G-19

Thus, 

) 1( 22% 11%) .0 808 .0 549 (MMTCO E)

1 22%

1 95%

95( %

) 1( )

1

1

(

2

11 12 BAU

11

2

prop 2

× − − × =

−

−

= +

⋅ − − ⋅

−

−

= + P P E

P

P

E P

. (4.3.11) 

The annual emission reductions are 

.0 808 .0 549 .0 259 (MMTCO E) 2

prop BAU prop

= − =

ER = E − E

. (4.3.12) 

Having self-sealing valve installed on the cans, managing the can return / 

recycling, and handling the deposit would cause additional costs, which would 

most probably be passed on to consumers in the form of price increase of R31

per can. Those who do not return the cans would lose the deposit of R32 per can. 

Per Assumption 12, no additional costs to the consumers would occur as a result 

of the education components. 

The number of DIY recharging is the same as under BAU (NR,BAU). 

9 (times)

1

9

1

adj

R,prop

= =

=

Y

Y

N

. (4.3.13) 

The annual costs for a vehicle whose owner returns the used cans are 

18 20. (dollars)

1

3.1 13( )1

( )

1

C 1 21

1,prop

=

× +

=

⋅ +

=

Y

N R R

C

. (4.3.14) 

Note that every recharge uses the same number of cans as under BAU 

(Assumption 13). 

The lifetime costs for such a vehicle are 

9 18 20. 163 80. (dollars)

1,L,prop adj 1,prop

= × =

C = Y ⋅C

. (4.3.15) 
G-20

The annual costs for a vehicle whose owner does not return the used cans are 

31 20. (dollars)

1

3.1 13( 1 10)

( )

1

C 1 21 22

2,prop

=

× + +

=

⋅ + +

=

Y

N R R R

C

. (4.3.16) 

The lifetime costs for such a vehicle are 

9 31 20. 280 80. (dollars)

2,L,prop adj 2,prop

= × =

C = Y ⋅C

. (4.3.17) 

Then the annual costs for all DIY vehicles are 

95% .1 404 18 20. 1( 95%) .1 404 31 20. 26 47. (million dollars)

1( )

all,prop 2 V ,1 prop 2 V ,2 prop

= × × + − × × =

C = P ⋅ N ⋅C + − P ⋅ N ⋅C

. (4.3.18) 

The annual extra costs for all DIY vehicles are 

26 47. 23 73. 74.2 (million dollars)

all,prop all,prop all,BAU

= − =

EC = C −C

. (4.3.19) 

The cost-effectiveness to consumers is 

10 58. (dollars/MTCO E)

.0 259

74.2

2

prop

all,prop

cons,prop

= =

=

ER

EC

CE

. (4.3.20) 

The annual revenue losses by small can industry are

RLprop = 0 . (4.3.21) 
G-21

4.3.3 Can Ban 

If a can ban is in place, a portion of the original DIY consumers would change 

their behavior based on costs, convenience and other personal preferences, but 

not the MVAC’s working conditions (Assumption 14). A fraction (P31) of the same 

leaky vehicles would be brought into professional shops for diagnosis, repair and 

recharge by MPro (in MMTCO2E) of fresh refrigerant. They originally would lose

50% of their nominal charge over Y1 years (Assumption 14) if DIY recharged. But 

now they would leak at reduced rates during Y2 years until they lose 50% of their 

nominal charge again. A second part (P32) of the leaky vehicles would be taken 

to professional shops for recharge without repair. The serviced AC will then leak 

at the same rate as DIY (Assumption 14), but during a modified (prolonged) 

period. This is because DIY generally undercharge AC due to lack of equipment 

and skills to know the proper amount of effective charge. On the contrary, 

professional technician can charge AC to its nominal level. Defining F1 as the 

ratio of charge to be leaked out before next servicing from a professionally 

recharged AC to that from a DIY recharged AC, a professionally recharged AC 

needs another recharging after a period of F1·Y1. Another fraction (P33) of the 

leaky vehicles would be taken to professional shops for topping off using small 

cans or cylinder and manifold. According to Assumption 15, they will be charged 

by MDIY and the charge will leak out during Y1 years, essentially the same as DIY. 

A fourth portion (P34) of the vehicles would still be DIY recharged with refrigerant 

obtained from alternative ways, resulting in exactly the same emissions as under 

BAU (Assumption 14). The rest of the leaky vehicles would not get repair and 

recharge and hence would eventually go without AC, generating no refrigerant 

emissions. The total annual emissions should include not only the amount of 

fresh refrigerant effectively charged into the AC, but also the fresh refrigerant lost 

during servicing (DIY or professional) and due to container (can or cylinder) heels. 

11 12

1

DIY

34 V

1

DIY

33 V

35 36

1 1

Pro

32 V

2

Pro

31 V

ban 1 1 P P

Y

M

P N

Y

M

P N

P P

F Y

M

P N

Y

M

P N

E

− −

⋅ ⋅ + ⋅ ⋅

+

− −

⋅

⋅ ⋅ + ⋅ ⋅

= , (4.3.22) 

where P35 and P36 are the fractions of fresh refrigerant lost due to can heel and 

during servicing, respectively, during professional recharging. Note that P36 is 

assumed to be negligible in this analysis. 

Define 

2

DIY

Pro F

M

M

= . 
G-22

Then 

) 7% 19%)] .0 808 .0 402 (MMTCO E)

4.1

23%

32%

6

1

6.1 (

1 2% 0%

1 22% 11%

[

( ) )]

1

1

[

2

33 34 BAU

1

32

31

2

1

2

35 36

11 12

ban

× × × + + + × =

− −

− −

=

⋅ ⋅ ⋅ + + + ⋅

− −

− −

= P P E

F

P

P

Y

Y

F

P P

P P

E

. (4.3.23) 

The derivation of P31, P32, P33, P34, F1, and F2 can be found in 4.5.3 and 4.5.4. 

The annual emission reductions are 

.0 808 .0 402 .0 405 (MMTCO E) 2

ban BAU ban

= − =

ER = E − E

. (4.3.24) 

The number of professional servicing that involves repair in a vehicle’s lifetime is 

5.1 (times)

6

9

2

adj

R,rep

= =

=

Y

Y

N

. (4.3.25) 

The annual costs for such a vehicle are 

108 33. (dollars)

6

650

2

31

1,ban

= =

=

Y

R

C

. (4.3.26) 

The lifetime costs for such a vehicle are 

9 108 33. 975 (dollars)

1,L,ban adj 1,ban

= × =

C = Y ⋅C

. (4.3.27) 

The number of professional recharging that does not involves repairs in a 

vehicle’s lifetime is 

4.6 (times)

4.1 1

9

1 1

adj

R,rec

=

×

=

⋅

=

F Y

Y

N

. (4.3.28) 
G-23

The annual costs for such a vehicle are 

71 43. (dollars)

4.1 1

100

1 1

32

2,ban

=

×

=

⋅

=

F Y

R

C

. (4.3.29) 

The lifetime costs for such a vehicle are 

9 71 43. 642 86. (dollars)

2,L,ban adj 2,ban

= × =

C = Y ⋅C

. (4.3.30) 

The number of professional topping off in a vehicle’s lifetime is the same as 

under BAU (NR,BAU). 

9 (times)

1

9

1

adj

R,top

= =

=

Y

Y

N

. (4.3.31) 

The annual costs for such a vehicle are 

100 (dollars)

1

100

1

32

3,ban

= =

=

Y

R

C

. (4.3.32) 

The lifetime costs for such a vehicle are 

9 100 900 (dollars)

3,L,ban adj 3,ban

= × =

C = Y ⋅C

. (4.3.33) 

The number of DIY recharging using refrigerant obtained through alternative 

ways is the same as under BAU (NR,BAU). 

9 (times)

1

9

1

adj

R,alt

= =

=

Y

Y

N

. (4.3.34) 
G-24

The annual costs for such a vehicle are 

25 35. (dollars)

1

3.1 1( 50%) 13

1( )

1

C 37 1

4,ban

=

× + ×

=

⋅ + ⋅

=

Y

N P R

C

, (4.3.35) 

where P37 is the percentage of cost increase for those who seek alternative ways 

of obtaining refrigerant. 

The lifetime costs for such a vehicle are 

9 25 35. 228 15. (dollars)

4,L,ban adj 4,ban

= × =

C = Y ⋅C

. (4.3.36) 

Note that the owners for the rest of the original DIY vehicles would choose to 

forgo AC under can ban, thus incur no costs. 

The annual costs for all original DIY vehicles are 

.1 404 32( % 108 33. 23% 71 43. 7% 100 19% 25 35. ) 88 36. (million dollars)

( ) V 31 1,ban 32 2,ban 33 3,ban 34 4,ban

all,ban 31 V 1,ban 32 V 2,ban 33 V 3,ban 34 V 4,ban

= × × + × + × + × =

= ⋅ ⋅ + ⋅ + ⋅ + ⋅

= ⋅ ⋅ + ⋅ ⋅ + ⋅ ⋅ + ⋅ ⋅

N P C P C P C P C

C P N C P N C P N C P N C

.(4.3.37) 

The annual extra costs for all original DIY vehicles are 

88 33. 23 73. 64 62. (million dollars)

all,ban all,ban all,BAU

= − =

EC = C −C

. (4.3.38) 

The cost-effectiveness to consumers is 

157 85. (dollars/MTCO E)

.0 405

64 62.

2

ban

all,ban

cons,ban

= =

=

ER

EC

CE

. (4.3.39) 

The annual revenue losses by small can industry are

13 24 98. (million dollars)

95%

.1 826

1

0

BAU

ban

= × =

= ⋅ R

P

S

RL

. (4.3.40) 

Note that the above equation accounts for the revenue from the can sales to 

professional servicing that would be lost in case of can ban. Also note that the 
G-25

potential revenue increase through sales via internet or from out-of-state is not 

included per Assumption 16. 

4.4 Detailed Summary of Results 

Table 3: Detailed Emissions and Economic Impact of Regulatory Proposals 

BAU Staff 

Proposal*

Can 

Ban 

Annual Can Sales to DIY (million cans) 1.8 1.8 NA 

Annual Emissions (MMTCO2E) 0.81 0.55 0.40 

Annual Emission Reductions (MMTCO2E) NA 0.26 0.41 

Annual Costs for All Original DIY Vehicles (million dollars) 23.73 26.47 88.36

Annual Extra Costs for All Original DIY Vehicles (million dollars) NA 2.7 64.6 

Cost-effectiveness to Consumers (dollars/MTCO2E) NA 11 159 

Annual Revenue Loss (million dollars) NA 0 25 

* Calculation based on a can return rate target of 95% 
G-26

4.5 Derivation of Key Independent Parameters 

4.5.1 Y1

Definition

The average interval between two DIY recharging is estimated by several 

approaches and data sources in this document. In most cases, it is calculated 

based on responses from surveyed individuals about their recharge intervals. It 

needs to be noted that the average recharge interval should not be defined as 

the straight mean of the recharge intervals from all the samples because this 

does not make physical sense. Rather, it should be defined as the reciprocal of 

the average leak rate and the average leak rate is the mean of the leak rate for 

all responses. In other words, it is the harmonic mean of the recharge intervals of 

all the samples: 

∑=

=

N

Y N Y i 1 i

1 1 1

. (4.5.1) 

This is because, by definition, the average delayed emissions per vehicle are the 

arithmetic mean of the delayed emissions of all the vehicles under consideration: 

∑=

=

N

E

N

E

i 1

i

1

, (4.5.2) 

where 

i

i

Y

M

E = , (4.5.3) 

and 

Y

M

E = , (5.5.4) 

where M is the effective charge that is to be emitted over the period of Yi, which 

will incur the next recharge. Equations (4.5.2) through (4.5.4) lead to Equation 

(4.5.1). 

In case the intervals are accompanied with percentages of DIY, the mean 

becomes weighted mean: 

∑=

= ⋅

N

Y

P

Y i 1 i

i

1 1

. (4.5.5) 
G-27

ARB El Monte Survey

During the ongoing study on non-professional servicing of MVAC sponsored by 

ARB, Denis Clodic’s team interviewed 16 people who participated in the study. 

10 out of them provided relevant responses. Out of these 10, 3 responded with 

an ambiguous answer, “long time ago”. The vintage of their vehicles was as early 

as 1996 and as late as 2003. These 3 responses are hence deemed invalid and 

excluded from the analysis. The valid responses are compiled in Table 4. 

Table 4: Recharge Interval in ARB El Monte Survey 

Vintage Time of last recharge Recharge interval 

(months) 

1999 5 months ago 5 

1994 4 months ago 4 

1997 10 years ago 120 

1994 1994 156 

2001 4 years ago 48 

2004 3 years ago 36 

1997 1 year ago 12 

Using Equation (4.5.1), the average recharge interval is 11.7 months. 

2008 ARPI DIY Survey

ARPI conducted a survey in May, 2008 in California to characterize DIY 

consumer profiles. 200 survey were handed out in participating Autozone stores 

in Southern California and 20 responses were received (ARPI, 2008c). Two of 

the questions are related to estimating recharge intervals. The relevant results 

are compiled in Table 5. 

Table 5: Recharge Interval in 2008 ARPI DIY Survey 

Time of last 

recharge 

Recharge interval 

(months) Percentage Combined Percentage 

Normalized 

Percentage

< 3 months 3 5% 5% 5.4% 

3 months to 1 year 7.5 20% 20% 21.6% 

1 to 2 years 18 30% 30% 32.4% 

>2 years 72 15% 37.5% 40.5% 

never 30% 

Time of owning 

the vehicle Percentage Percentage: never recharged

<1 yr. 25% 7.5% 

1 to 2 yrs. 35% 10.5% 

2 to 3 yrs. 15% 4.5% 

3 to 4 yrs. 5% 1.5% 

> 4 yrs. 20% 6.0% 

Own for >1yr.; 

never recharged 22.5% 
G-28

Although 30% of the respondents said that they never recharged their AC before, 

it is noticeable that most of the survey participants have not own their cars for 

very long. As the second part of the table shows, 80% of these people have their 

cars for less than 4 years. Therefore, having never charged does not necessarily 

mean the recharge interval would be very long (longer than 4 years). Assuming 

the vehicle ownership profile holds true for those who never charged their AC, 

7.5% own their vehicle for less than one year and never charged the AC, and 

22.5% own their vehicle for more than one year and never charged the AC. To 

be conservative, add the 22.5% to the 15% that had their last recharge more 

than 2 years ago, and assign a 6-year recharge interval for the total 37.5%. 

Exclude the 7.5% that have owned their vehicle for less than a year and never 

recharged the AC, and normalize the rest of the population. Using Equation 

(4.5.5), the average recharge interval is 14.2 months. 

Frost and Sullivan Study

Commissioned by the ARPI, the Frost and Sullivan Co. conducted an online 

survey to investigate consumer purchase and usage behavior of small cans 

(Frost and Sullivan, 2006). Its California sample includes 400 respondents. The 

questionnaire did not explicitly ask about the recharging intervals. However, this 

information can be derived from the response to some other questions when 

making a few assumptions. 

According to the study, out of the 400 respondents, 38% or 152 of them generally 

would not use the full can of HFC-134a. Since whether a full can is used is a 

natural outcome of the recharging process, instead of an arbitrary decision, any 

other aspects of the can usage of these 152 people should be representative of 

the California respondents as a whole. So we only need analyze these 152 

samples. Among them, 62% or 95 would store the partial can, and the rest 38% 

or 57 would dispose of it. Of the 95 people that stored the partial cans, 22% of 

them said that they had not tried to re-use them. This can be conservatively 

interpreted as the fraction of people that had only recharged once. 

The study provides the storage period for those who would store the partial cans. 

This information is included in the first and third columns of Table 6. Each 

storage period range is assigned a storage period as the middle value of the 

range in the second column, where storage period of longer than 18 months is 

conservatively assigned the value of 72 months. Some of them are first time DIY 

and we need to exclude them when estimating the recharge intervals. However, 

12% of the people stored the cans for over a year and they are certainly not the 

first time DIY. This is because the survey respondents all had recharged AC in 

the past 12 months. If they are the first time users, the recharge events 

happening within the 12 months were their only experience and their storage 

periods are definitely less than 12 months. We have shown that 22% of the 

people had only charged once. This translates into 25% out of the 88% whose 

storage periods were less than a year (25% = 22% ÷ 88%). Evenly allocating 
G-29

25% to all these 88% people, we get the percentage of the first time DIY in 

column 4, totaling 22% as expected. Only the rest 78% are the non-first time DIY, 

which is tabulated in column 5 and normalized in column 6. Finally, we use 62% 

to adjust the normalized percentages since 62% of all DIY consumers would 

store the cans. 

Table 6: Storage Period for People Who would Store Partial Cans 

Storage 

Period 

Range 

Storage 

Period 

(months) 

Percent of 

DIY 

First Time 

DIY 

Non-first 

Time DIY 

Normalized 

Non-first 

Time DIY 

Non-first 

Time DIY 

Multiplied 

by 62% 

0-3 mon 3 27% 7% 20% 26.0% 12.6% 

3-6 mon 4.5 19% 5% 14% 18.3% 8.8% 

6-9 mon 7.5 25% 6% 19% 24.0% 11.6% 

9-12 mon 10.5 17% 4% 13% 16.4% 7.9% 

12-18 mon 15 6% 0% 6% 7.7% 3.7% 

>18 mon 72 6% 0% 6% 7.7% 3.7% 

Total of First 4 

Lines 88% 22% 

Total of First 4 

Lines Divided 

by 22% 

25% 

On the other hand, of all the California respondents (348 valid responses), 42% 

had only recharged their present and past vehicles once. As an approximation, 

we assume all the recharges happen to their present vehicles. This percentage 

should hold true for the 152 people that would not use up the full cans. Therefore, 

22%× 62% + Pdisp ×38% = 42% , 

where Pdisp is the percentage of the first time DIY out of those who would dispose 

of the can. And 

Pdisp = 75%. 

It indicates that most people disposing of partial cans are first time users. This is 

consistent with intuition since experienced consumers would know that once the 

vehicle starts needing recharge, it is likely that it has some leaking problem and 

may need repeated recharge within a certain time frame. 

Assuming disposing of or store partial cans is more related to personal 

preference than recharging practices, we can apply the same apportionment as 

in Table 6 for those who choose to dispose of partial cans by “virtual storage 

period”. This is the period that they would store cans should they choose to store 

the cans. This is shown in Table 7. 
G-30

Table 7: Virtual Storage Period for Those Who would Dispose of Partial 

Cans 

Storage 

Period 

Range 

Storage Period 

(months) 

Percent 

of DIY 

First Time 

DIY 

Non-first 

Time DIY 

Normalized 

Non-first 

Time DIY 

Non-first 

Time DIY 

Multiplied 

by 38% 

0-3 mon 3 27% 23% 4% 16.0% 1.5% 

3-6 mon 4.5 19% 16% 3% 11.2% 1.1% 

6-9 mon 7.5 25% 21% 4% 14.8% 1.4% 

9-12 mon 10.5 17% 14% 3% 10.0% 1.0% 

12-18 mon 15 6% 0% 6% 24.0% 2.3% 

>18 mon 72 6% 0% 6% 24.0% 2.3% 

Total of First 4 

Lines 88% 75% 

Total of First 4 

Lines Divided 

by 75% 

85% 

Adding the last columns of the above two tables, we obtain the storage period for 

the overall California samples (Table 8). It is important to note that this study 

restrict the survey panel to those who had charged their MVAC during the last 12 

months. Thus, the survey panel members with recharge intervals of less than 12 

months are not filtered. But for those with recharge intervals of more than 12 

months, only a fraction will be able to participate in the survey. For example, for 

the group that has recharge intervals of 6 years, approximately 1/6 of them would 

have performed recharging during the last 12 months and would have been 

captured by the survey. Their percentages in the following table should then be 

multiplied by 6 to account for that. This is also true for the group with recharge 

interval of 15 months. After this adjustment and then normalization, around half 

of the samples have a recharge interval of more than a year. Using Equation 

(4.5.5), the average recharge interval is 8.5 months. 

Table 8: Overall Storage Period 

Storage 

Period 

Range 

Storage 

Period 

(months) 

Combined 

Non-first 

Time DIY 

Adjusted 

Combined 

Non-first 

Time DIY 

Normalized 

Non-first 

Time DIY 

0-3 mon 3 14.1% 14.1% 15.8% 

3-6 mon 4.5 9.9% 9.9% 11.1% 

6-9 mon 7.5 13.0% 13.0% 14.6% 

9-12 mon 10.5 8.9% 8.9% 9.9% 

12-18 mon 15 6.0% 7.5% 8.4% 

>18 mon 72 6.0% 36.0% 40.3% 
G-31

NPD Sales Data

The NPD Automotive Aftermarket Industry Monitor provides cashier transaction 

information from the U.S. auto parts chain retailers (NPD, 2008). The data come 

from nine participants including Advance, AutoZone, CSK/Murrays, PepBoys, 

O'Reilly’s, CarQuest, NAPA, Strauss Auto and Parts Alliance. As shown in Table 

9, in 2006 and 2007, average annual sales of HFC-134a units without charging 

kits were 14 million. Given that every recharging uses about 1.3 cans on average, 

this suggests 11 million DIY recharging operations each year. The Average 

annual sales of charging kits were just over 1 million. Assuming a vehicle’s 

“effective lifetime” during which it needs recharging is 9 years and every DIY user 

only purchase one charging kit and use it throughout his vehicle’s lifetime, the 

number of DIY vehicles should be equal to the total sales of charging kits in 9 

years, which is about 10 million. Thus, on average, a DIY vehicle gets 1.1 

recharging per year and the recharge interval is 10.8 months. 

Table 9: NPD Data on HFC-134a Units Sold in the U.S. 

 2006 & 2007 Total

Total HFC-134a Units without Charging Kits 14,079,386 

AC Charging Kits 1,086,872 

DIY Recharge Operations per Year 10,830,297 

AC Charging Kits Sold in 9 Years 9,781,848 

DIY Vehicles 9,781,848 

Recharges per Vehicle per Year 1.1 

Summary

The recharge interval estimates range from less than three quarters to slightly 

over 14 months (Table 10). Therefore, it is reasonable to assume a recharge 

interval Y1 = 1 year. 

Table 10: Summary of Recharge Interval Estimates 

Data Source(s) Sample Size Recharge Interval 

Estimate (months) 

ARB El Monte Survey 7 11.7 

2008 ARPI DIY Survey 20 14.2 

Frost and Sullivan Study 152 8.5 

NPD Survey 10.8 

4.5.2 P0

SAE supplied data that indicate that of all the HFC-134a used in MVAC 

nationwide in 2003, factory fill, 30-lb cylinders and small cans share 30%, 39% 

and 31%, respectively (Atkinson, 2008a). 30-lb cylinders are apparently 

exclusively used by professional servicing. But some professional technicians 

also use small cans, which is about 3.5% of the total usage by professional 
G-32

shops (MACS, 2008). Thus, out of all the HFC-134a used in MVAC, the 

percentage of HFC-134a in small cans used by professional shops is 

39% 4.1 %

1 5.3 %

5.3 %

× =

−

. 

So the percentage of small cans used by professional servicing in relation with 

the total small can usage is 

6.4 %

31%

4.1 %

= . 

Therefore, 96.4% of small cans are sold to DIY. Rounding it off, we have P0 = 

95%. 

4.5.3 P31, P32, P33, and P34

A study of small can consumers commissioned by the ARPI estimates that 12% 

of former DIY owners would opt to have no air conditioning rather than go to a 

professional shop, 49% would go to the professional shop, and 39% would look 

for other options of obtaining refrigerant (Frost and Sullivan, 2006). The 39% of 

consumers seeking alternative options will contribute to illegal internet or out of 

state sales, but given the inconvenience of doing that, it is unlikely that all of 

them will have the perseverance to circumvent the can ban. The true rate of DIY 

circumventing the ban will probably be somewhere between 0% and 39%. In the 

absence of further data on which to assign a fraction, we take the midpoint of this 

range, or 19%, to maximize the probability of being close to reality. We assume 

that the remainder of those looking for alternative sources of HFC-134a will 

choose one of the legitimate options which are: obtain professional repairs, 

obtain professional recharge without repair, obtain professional top off, forgo air 

conditioning, or go to professional servicing without deciding on actions. We 

assign the rest half (20% of total) of the former DIY equally among those five 

legitimate options: 4% forgo air conditioning; 4% go to the shop for repair and 

recharge; 4% go to the shop for recharge without repair; 4% go to the shop for 

topping off; and 4% go to the shop undecidedly. The percentages in each 

category become: forgo air conditioning 12% + 4% = 16%; go to the shop 

undecidedly 49% + 4% = 53%; go to the shop with the specific objective of repair 

4%; go to the shop specifically for recharge without repair 4%; go to the shop 

specifically for topping off 4%; and obtain HFC-134a by alternative means 19%. 

A 2005 MACS study showed the choices of customers who currently visit 

professional shops for diagnosis and repair (Atkinson, 2008b). The study 

surveyed 7 service facilities located in Pennsylvania, Ohio, Arizona, California 

and Florida and included over 1,400 repair orders. In that study, among those 

with refrigeration circuit problems, 88% chose to have their system repaired or 

recharged, 7% chose to simply be topped off, and the other 5% choose to reject 
G-33

recharges and forgo air conditioning. The first two categories, adding up to 95%, 

represent all the operations that involve adding refrigerant. An IMR Continuing 

Consumer Auto Maintenance Survey (CCAMS) data supplied by ARPI (ARPI, 

2008a) suggest that of all professional servicing that involve adding refrigerant, 

only 56% involves repair. This translates into 53% in context of the 95%, 

whereas the other 42% of the 95% are either topping off (7%) or recharge 

without repair (42% - 7% = 35%). 

Assuming the 53% of consumers described in the first paragraph who go to 

professional shops without deciding on actions would behave the same way as 

normal customers at professional shops, they are reapportioned into categories 

as described in the preceding paragraph: 28% of former DIY consumers have AC 

repaired; 19% get recharge without repair; 3% receive topping off; and another 

3% forgo AC. Recombining them with those who already have specific goals, P31

= 32% get professional repair, P32 = 23% receive professional recharge, P33 = 

7% top off at professional servicing, P34 = 19% continue DIY recharging AC using 

refrigerant obtained through alternative means, and the other 19% forgo AC. The 

figure below shows how the various fractions were apportioned and combined, 

with the final values on the right. 

Figure 5. DIY Behavior Change under Can Ban 

4.5.4 F1 and F2

The average nominal charge size of passenger vehicles in the U.S. is 824 grams 

(Thundiyil, 2008b). It assumed the AC average to 50% empty when brought in to 

the professional servicing facility for recharge (Assumption 5), which indicates 

that 412 grams of refrigerant remains in the AC. 

Every DIY recharge uses 445 grams of refrigerant (all fresh), with 98 grams 

(22%), 49 grams (11%), and 298 grams (67%) as can heel, servicing loss, and 

effective charge, respectively. Apparently DIY on average recharge AC at 86% 

(412 grams remaining refrigerant + 298 grams fresh refrigerant) of nominal level. 

A DIY recharged AC has 298 grams of refrigerant to lose before the next 

recharge is needed. 

Original Apportioned Combined Reapportioned Recombined

28% pro repair

19% pro recharge

4% pro shop 3% pro top off

4% pro repair 3% forgo AC

4% pro recharge 4% pro repair 4% pro repair

4% pro top off 4% pro recharge 4% pro recharge

4% forgo AC 4% pro top off 4% pro top off

19% leakage 19% leakage 19% leakage 19% leakage

12% forgo AC 12% forgo AC 16% forgo AC 16% forgo AC 19% forgo AC

39% alternative

ways

49% pro shop 49% pro shop 32% pro repair

23% pro recharge

7% pro top off

53% pro shop
G-34

In comparison, a professional technician has the equipment and skills to restore 

AC charge to its nominal level, rendering more refrigerant (412 grams) in the 

systems to be emitted before the next servicing is needed. When no repair is 

conducted, the recharged AC will leak at the same rate as a DIY recharged AC, 

but at a prolonged period. The recharge interval for a professionally recharged 

AC to that for a DIY recharged AC is 

4.1

298

412 F1 = = . 

It should be noted that during professional servicing (with or without repair), the 

amount of fresh refrigerant effectively charged into AC is not 412 grams because 

the remaining refrigerant needs first to be recovered and stored in a cylinder. 

Then it will be recharged back into the AC. These operations will incur losses due 

to servicing losses and cylinder heels. The refrigerant lost during incomplete 

recovery is by far the main source of servicing losses. For purpose of analysis, 

we assume the refrigerant recovery rate by professional servicing using the 

current prevailing equipment and practices is 85%. Thus, 62 grams (15% of 412 

grams) will be lost due to incomplete recovery. A new SAE standard for 

refrigerant recovery and recharge, J2788, has taken into effect, to replace the old 

SAE J2210 standard. Using the equipment and practices compliant with the new 

standard, the recovery rate will be increased to at least 95% (about 21 grams of 

servicing loss). However, there is no requirement for the professional servicing to 

replace their current recovery machines, and the phase-in of the new machines 

will likely be slow. The recovered 350 grams will be stored in cylinder for future 

use. Not all of them will be effectively charged into AC during the next servicing 

due to cylinder heels. The U.S. EPA Disposable Container Heel Testing Study 

found that the cylinder heel in professional servicing is about 1.8% (U.S. EPA, 

2007). This translates into about 7 grams loss in cylinder heel out of the 

recovered 350 grams. The rest of 343 grams will be effectively charged into AC 

during the next recharge. To add up to the nominal charge of 824 grams, another 

481 grams of fresh refrigerant needs to be effectively charged into the AC, which 

will cause another 10 grams of losses in cylinder heel. Therefore, the ratio of 

fresh refrigerant effectively charged into AC during professional recharging to 

that during DIY recharging is 

6.1

298

481 F2 = = . 
G-35

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G-36

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G-37

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