Office of Transportation and Air Quality

EPA-420-F-13-008

April 2013

Diesel Emissions Quantifier (DEQ) 

Frequently Asked Questions (FAQs)

Revised April 4, 2013
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Table of Contents

Administrative ............................................................................................................................................................3

Logging In................................................................................................................................................................3

Saving Results.........................................................................................................................................................3

Changing Your Password ........................................................................................................................................3

Activating Your Account.........................................................................................................................................4

Uses and Limitations ..................................................................................................................................................4

Light-duty Vehicles.................................................................................................................................................4

Congestion Mitigation and Air Quality Improvement Program (CMAQ) ...............................................................4

State Implementation Plans (SIPs) .........................................................................................................................4

Fuel Savings/Fuel Economy Benefits......................................................................................................................4

CO2 ..........................................................................................................................................................................4

C3 Marine ...............................................................................................................................................................4

Black Carbon...........................................................................................................................................................5

Defaults and Emission Rates ......................................................................................................................................5

Defaults ..................................................................................................................................................................5

Emission Rates........................................................................................................................................................5

Calculations and Units................................................................................................................................................6

Calculations ............................................................................................................................................................6

Units .......................................................................................................................................................................6

Use in the Grant Process............................................................................................................................................6

Choosing a Calculator.............................................................................................................................................6

Cost-Effectiveness ..................................................................................................................................................7

Health Benefits...........................................................................................................................................................9

Pollutants and Health Effects.................................................................................................................................9

Counties............................................................................................................................................................... 10

Calculations and Accuracy................................................................................................................................... 11

Outputs and Uses................................................................................................................................................ 11

Cost Benefits (Explanation and Troubleshooting)............................................................................................... 12

Other.................................................................................................................................................................... 13
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Data Entry................................................................................................................................................................ 13

Multiple Technologies......................................................................................................................................... 13

Fuel Types............................................................................................................................................................ 13

Replacement........................................................................................................................................................ 14

Truck Stop Electrification..................................................................................................................................... 14

Trailer Refrigeration Unit..................................................................................................................................... 14

Uncertainty, Missing Information, Averaging, and Diverse Fleets...................................................................... 15

Fleets ................................................................................................................................................................... 15

Baseline Emissions............................................................................................................................................... 15

Idle Reduction...................................................................................................................................................... 16

Maintenance and Operating Costs...................................................................................................................... 16

Vehicle Definitions and Classes........................................................................................................................... 16

Verification Information...................................................................................................................................... 17

Input Errors.............................................................................................................................................................. 17

Vehicle Groups .................................................................................................................................................... 17

Model Year .......................................................................................................................................................... 17

Horsepower......................................................................................................................................................... 17

Replacement (Engine and Vehicle)...................................................................................................................... 17

Technologies........................................................................................................................................................ 18

Fuels..................................................................................................................................................................... 18

Currently Documented Errors................................................................................................................................. 18

Appendix: Grouping Vehicles for Calculations in the DEQ...................................................................................... 20
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Administrative

Logging In

Question: I’m having trouble logging in. 

Answer: Close the DEQ and try again. If this doesn’t work, delete your internet browser's history and cookies 

(usually found under “tools”) and try logging in. If you still can’t log in, please send an email to 

cleandiesel@epa.gov with “DEQ User Account Problem” in the Subject Line, and include your DEQ user 

account email. Meanwhile, you can create a new username and password or use the DEQ without 

logging in.

Question: When I try to access the DEQ, I receive an error message. 

Answer: The server that hosts the DEQ can get overloaded when too many users are trying to log on at the 

same time. DEQ traffic will be high around the close of any National Clean Diesel grant competition. 

Try using the DEQ during off-peak hours (early morning, late evening or weekends). Or you can try 

closing your browser and re-accessing the DEQ using a different browser or without logging in. 

If you still can’t access the DEQ or cannot get through a calculation without the DEQ sending an error 

message, send an email to cleandiesel@epa.gov with “Cannot Access or Complete DEQ run” in the 

Subject Line. Please include a screenshot of the error message and your user account email (if you 

logged in). 

If you can replicate the error message, it’s helpful to include all of the inputs entered before the DEQ 

sent the error message. If you can’t replicate the error, please provide a description of the calculation 

you were trying to make. 

Saving Results

Question: Is there a way to save more than three “fleets” in the DEQ under a single login account? 

Answer: No. However, each “fleet” (with the exception of marine vessels) can accommodate up to 30 

“vehicle groups”. Currently, each marine vessel must be a separate “fleet” (each vessel can have up to 

five marine engines). You may open multiple user accounts, but each account must have a unique email 

address. 

Question: Sometimes when trying to save DEQ results in an Excel format, the data is saved as a text (txt) file. 

How can I get the results into Excel format?

Answer: The DEQ allows users to save both the Summary Results and Detailed Results in Excel or CSV 

formats. Sometimes files won’t save properly because of the download settings of your browser and/or 

computer. 

If your results are being saved as a text file, re-save or rename the file with an “xls” extension and Excel

should be able to open it. If you need the results in CSV format, save in the CSV format directly from the 

DEQ, instead of saving to Excel and then converting to CSV. 

Changing Your Password

Question: How do I change my DEQ password? 

Answer: To change your password, go to www.epa.gov/cleandiesel/quantifier, select the "Use the 

Quantifier" tab, log in, and click on “Edit Profile”. 
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Activating Your Account 

Question: I’ve submitted my account registration information, but I am unable to log in. How does my 

account get activated?

Answer: You should have received an activation email with a validation link. You must click on this 

validation link to activate your account. 

The activation email may have been caught in your SPAM filter or your email address may have been

mistyped on the registration form. If you can’t find the activation email in your SPAM filter, try 

registering the account again. 

Occasionally the DEQ server doesn’t recognize an email address ending in “.net”. We are working to 

resolve this and suggest that you register with an email address that ends with “.gov, .edu, or .com” if 

possible. 

Uses and Limitations

Light-duty Vehicles

Question: Can the DEQ be used for light-duty projects (i.e. diesel pickups)?

Answer: No. The DEQ calculates emission reductions for medium-heavy and heavy- heavy-duty vehicles 

only. The Motor Vehicle Emissions Simulator (MOVES) model at www.epa.gov/otaq/models/moves can 

be used to calculate emission reductions for light-duty or heavy-duty vehicles. 

Congestion Mitigation and Air Quality Improvement Program (CMAQ)

Question: Can the DEQ be used to estimate benefits for the Congestion Mitigation and Air Quality 

Improvement Program (CMAQ)?

Answer: Yes, the DEQ is an estimation tool that may be used for CMAQ planning purposes.

State Implementation Plans (SIPs)

Question: Can the DEQ be used for State Implementation Plan (SIP) calculations?

Answer: No. When the DEQ estimates emission reductions, some default values are used. SIP and 

conformity calculations require more sophisticated modeling tools that use specific inputs. Please refer 

to your SIP and conformity guidance documents or contact your regional EPA office at 

www.epa.gov/cleandiesel/ncdc-cmt.htm for more information. 

Fuel Savings/Fuel Economy Benefits

Question: Does the DEQ provide information on fuel savings?

Answer: No. However, when the quantity of saved diesel fuel is input to the DEQ, it can calculate the CO2 

emission reductions. 

CO2

Question: Would replacing an engine reduce CO2 (carbon dioxide) emissions? 

Answer: Maybe. In addition to reductions from burning less fuel, there is a potential for CO2 reduction from 

the new engine. Because engines are not currently certified for CO2, the DEQ relies only the amount of 

fuel reduced to estimate CO2 reductions.

C3 Marine 

Question: How can I calculate emission reductions for C3 marine engines in ocean-going vessels?
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Answer: C3 marine engines are currently beyond the scope of the DEQ. Please see “Current Methodologies 

in Preparing Mobile Source Port-Related Emission Inventories” at 

www.epa.gov/cleandiesel/publications.htm for help in calculating these emission reductions or contact 

EPA’s Helpline at 1-877-NCDC-FACTS or cleandiesel@epa.gov. 

Black Carbon

Question: Black carbon, also known as elemental carbon, is a potent climate change agent found in 

diesel particulate matter. Does EPA have plans to include black carbon in the DEQ so its climate 

change impacts can be estimated? 

Answer: The agency is still working on guidance regarding black carbon. At this time, there are no definite 

plans to include black carbon in the DEQ.

Defaults and Emission Rates

Defaults

Question: Can you provide more information about the DEQ default values?

Answer: The DEQ default values were compiled using various reports and models. For more information, see 

the DEQ Default Values document at www.epa.gov/cleandiesel/documents/420b10035.pdf. 

Question: How does the DEQ calculate the life of a vehicle? Can that value be overridden? 

Answer: For on-highway vehicles, the lifetime is set at 30 years based on our modeling. For nonroad 

applications, the lifetime is usually shorter but will vary depending on equipment type and horsepower. 

The default values for the life of a vehicle cannot be overridden in the DEQ.

Emission Rates

In November 2010, EPA updated DEQ emission rates for highway/on-road vehicles using data from the 

Mobile Vehicle Emissions Simulator (MOVES2010) at www.epa.gov/otaq/models/moves. MOVES2010 

incorporates a number of significant improvements over the old MOBILE6.2 rates, particularly in baseline 

emissions, activity data, and calculations used to estimate emissions in real-world driving conditions. 

For current and future highway/on-road projects, it is highly recommended that you use the MOVES2010 

emission rates by selecting retrofit year of 2011 or later.

Question: Which "Year of Retrofit Action" should I use if my project spans several years, for instance 2008 to 

2011? 

Answer: We recommend that you use MOVES2010 emissions rates by selecting 2011 or later as the "Year of 

Retrofit Action" for the entire project, even if the retrofit activity took place before 2011.

Question: What should I do if my project spans 2008 -2011 and my initial calculations used the old MOBILE 

6.2 emission rates in the DEQ? 

Answer: We recommend that you perform your final calculations using the new MOVES2010 emission rates

by choosing 2011 as your "Year of Retrofit Action". 

Question: My project has been completed and I’ve already done my calculations using the old DEQ 

numbers. Do I need to re-run the DEQ using 2011 as the "Year of Retrofit Action"? 

Answer: No. If your project is closed and you have already turned in your final report, there is no need to 

re-run the DEQ to update the emissions savings. 
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Question: What happens if I continue to use the old DEQ MOBILE 6.2 emission rates by selecting a “year of 

Retrofit Action” prior to 2011? 

Answer: You will not run into any problems using the DEQ. However, using the old MOBILE 6.2 numbers for 

your calculations will severely underestimate your emission reductions. 

Question: Why do DEQ emission factors vary from state to state for the same vehicle(s)?

Answer: The modeling tools used to generate emission factors for the DEQ take into account a variety of 

state- and county-specific characteristics such as climate, geography, roads, and population. These 

characteristics affect emission levels, causing them to differ by state and/or county. Neighboring states 

and counties may see smaller differences than those that are farther apart. 

For projects extending beyond a single state, select the state in which the majority of activity will take place. 

Question: Can EPA provide the emission factors and methodology used by the DEQ in a spreadsheet format 

so we can do the calculations ourselves? 

Answer: The DEQ derives its emission factors from EPA's standard modeling tools - MOVES2010 for onhighway calculations and NONROAD2008 for non-road calculations. For more information about these 

factors and models, please visit the MOVES www.epa.gov/otaq/models/moves or the NONROAD

www.epa.gov/otaq/nonrdmdl website. 

Calculations and Units

Calculations

Question: In calculating lifetime benefits, does the DEQ consider the remaining life of the vehicle or of the 

emission control device? 

Answer: Lifetime calculations are based on the remaining life of the vehicle, not the emission control device. 

EPA assumes that once a vehicle is retrofitted, it will remain retrofitted until the vehicle is retired. 

Question: Why do lifetime emission reductions use a vehicle’s remaining life instead of the full life of the 

vehicle? For instance, I am replacing a 20 year old school bus with a brand new one. The old bus has 10

years left while the new one has 30. The DEQ shows lifetime emission benefits for only the 10 remaining 

years of the old bus. Doesn’t this underestimate the emissions benefit of my new bus? 

Answer: The most the old bus will emit pollutants is its remaining life (10 years) - it will be replaced in 10 

years (when its remaining life is over) or some time before then. If it is replaced now (early 

replacement), the full 10 years of emissions will be reduced. That is the maximum that can be claimed. 

Units

Question: Does the DEQ give results in US short tons (2000 pounds), British long tons (2240 pounds) or

metric tons (2204 pounds)? 

Answer: Short tons.

Question: Can the DEQ separate particulate matter (PM) by PM2.5 and PM10? 

Answer: No. The DEQ only calculates PM2.5. 

Use in the Grant Process

Choosing a Calculator

Question: If the DEQ is not a good match for my project, are there other calculation tools I can use?

Answer: You can use any model you wish as long as you explain and document your calculations. 

Here are some other models for your consideration:
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1. Motor Vehicle Emission Simulator (MOVES) for on-road vehicles 

www.epa.gov/otaq/models/moves

2. NONROAD Model for nonroad engines, equipment, and vehicles 

www.epa.gov/otaq/nonrdmdl.htm 

3. SmartWay FLEET Tools for freight shippers, logistics companies, and rail, trucks, drayage and 

multi-modal carriers 

www.epa.gov/smartway/partnership 

4. Argonne National Laboratory GREET Model, for estimating vehicle lifecycles and carbon 

footprints. greet.es.anl.gov

Cost-Effectiveness

Question: How does the DEQ calculate cost-effectiveness? 

Answer: Cost-effectiveness can be calculated by the DEQ in two ways. Both calculations are simple and can 

also be done by hand. 

First, the DEQ can provide the dollar per ton of pollutant reduced for the entire project (Total Fleet Cost 

Effectiveness). For this calculation, input the cost of the whole project before you add a “Vehicle 

Group”.

Second, the DEQ can provide the dollar per ton of pollutant reduced for each unit (Capital Cost 

Effectiveness). For this calculation, enter the installation and unit costs per vehicle when you add a 

technology to your vehicle group. 

The Total Fleet Cost Effectiveness for the entire project appears only on the “Results” screen, while the 

Capital Cost Effectiveness per unit appears both on the “Results” screen and the Summary and Detailed 

results spreadsheets. 

 

1) Total Fleet Cost-Effectiveness

a) The DEQ totals the entire project funding amounts entered on the first DEQ screen (shown

below). This is the Total Project Cost.
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b) After the Vehicle Groups have been entered, the DEQ calculates the total lifetime emission 

reductions by pollutant (NOx, PM, HC, CO, and CO2) for the entire fleet. This is the Total Lifetime 

Tons Reduced. 

c) The DEQ then divides the Total Project Cost by the Total Lifetime Tons Reduced for each of the 

five pollutants. The results are shown in dollars/ton on the bottom of the Emission Results 

Page. The results are currently not shown in outputs that are downloadable in Excel and CSV

formats. However, it is a relatively simple calculation that can be done by hand using DEQ 

results. 

2) Capital Cost-Effectiveness is calculated using the installation and unit costs entered in the DEQ 

screen shown below. It does not include things like project administration costs and overhead.

Capital Cost-Effectiveness is calculated by adding the Unit Cost and Installation Cost for each 

technology and dividing the sum by the Total Lifetime Tons Reduced for each of the five pollutants.

This value is displayed both on the Emissions Results page and the outputs that are downloadable 

in Excel and CSV formats. 
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Health Benefits

Pollutants and Health Effects

Question: Which health effects of diesel PM2.5 are included in the cost/benefit calculation in the Health 

Benefits Module?

Answer: The benefits of reduced diesel emissions are based on avoided incidences of the following: 

• Premature mortality 

• Chronic bronchitis 

• Acute bronchitis 

• Upper and lower respiratory symptoms 

• Asthma exacerbation 

• Nonfatal heart attacks 

• Hospital admissions 
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• Emergency room visits 

• Lost work days 

• Restricted-activity days 

Question: Does the DEQ estimate reductions in total particulate matter or fine particulate matter (PM2.5)? 

Answer: The DEQ estimates reductions in PM2.5 and that is what is used for determining health benefits. For 

additional information, please refer to the Health Benefits Methodology at 

www.epa.gov/cleandiesel/documents/420b10034.pdf. 

Question: Is diesel particulate matter the only pollutant considered in the Health Benefits Module? 

Answer: Yes. There are likely benefits from reducing other pollutants, such as ozone and air toxics, but the 

DEQ cannot quantify these benefits at this time.

Counties

Question: How do I determine in which counties the emission reductions take place? 

Answer: The DEQ requires you to choose one state where the retrofits take place. For projects that span 

multiple states, such as long-haul trucks and locomotives, select the state where the majority of 

emissions are generated. 

Once the DEQ calculations are completed and you go to the Health Benefits tab, you can allocate the 

emission reductions among up to five counties (in multiple states). Note that the Health Benefits 

Module is not asking whether pollution from one county is drifting into another; it’s asking where the 

vehicles that are reducing their emissions are operating.

Question: My county is “flagged.” What does that mean? 

Answer: The Health Benefits Module will flag results for counties where there may be an under or over 

estimate of health benefits due to the migration of emissions into or out of the county. 

For counties with a large quantity of emissions flowing into the county, the results are flagged with the 

following message: Benefits estimates are “flagged” for this county, indicating that we have less 

confidence in these results due to a large amount of inter-county transport of emissions. The impacts 

estimation tool may be overestimating the benefits for emission reduction projects in this county, 

because it has relatively few emissions compared to surrounding areas. As a result, this county is likely to 

be a net importer of diesel emissions, and air quality is significantly affected by emissions in upwind 

counties. Please take this increased uncertainty into account when interpreting your results. 

For counties with a large quantity of emissions flowing out of the county, the results are flagged with 

the following message: Benefits estimates are “flagged” for this county, indicating that we have less 

confidence in these results due to a large amount of inter-county transport of emissions. The impacts 

estimation tool may be underestimating benefits for emissions reduction projects in this county, because 

it has a relatively high density of emissions compared to surrounding areas. As a result, this county is 

likely to be a net exporter of diesel emissions, and many of the benefits of reducing these emissions are 

likely to take place in downwind counties. Please take this increased uncertainty into account when 

interpreting your results.

Question: When I enter the same data for retrofit projects in different counties, why do I get different 

health benefits? 
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Answer: One of the main factors in determining the health benefits from reduced emissions is the 

proximity of people to where those emissions would have been generated. If a certain level of 

emission reduction is assigned to a census tract with a larger area, it will result in a lower 

concentration as the pollution is being spread over a greater area. The opposite is true as well. 

Assigning emission reductions to a smaller area census tract will result in higher concentrations. 

In addition, if a certain level of emission reductions is assigned to a less populated census tract, fewer 

people will be exposed resulting in a lower concentration ratio. Again, the opposite is true: emissions 

assigned to higher-populated tracts leads to a higher concentration ratio.

Calculations and Accuracy

Question: How are benefits of reducing diesel particulate matter calculated? 

Answer: The Health Benefits Module uses a county “look-up table”, which includes estimated benefits per 

ton of PM2.5 reduced for each county in the United States. 

The user answers a set of questions about their project. Once the DEQ estimates the emission changes, 

the Health Benefits Module uses the “look-up table” to estimate the health benefits associated with the

PM 2.5 reductions for the specified county. The combined monetary benefits of avoided mortality and 

avoided morbidity (i.e. non-fatal illness) for the selected counties are displayed. 

As part of the Quality Assurance process, EPA has also developed a table using on-road and nonroad 

diesel PM 2.5source tables. These tables and more are available in the Health Benefits Methodology at 

www.epa.gov/cleandiesel/documents/420b10034.pdf. 

Question: How accurate are the Health Benefits Module estimates? 

Answer: The methodology used to estimate health benefits was peer-reviewed both inside and outside EPA 

and many of the suggestions were incorporated. The module includes data and modeling from several 

existing EPA tools, such as the National Emissions Inventory (NEI), the National Air Toxics Assessment 

(NATA), and the Environmental Benefits Mapping and Analysis Program (BenMap). 

The benefits reflect reductions only in fine particulate matter. They do not include benefits from the 

reduction of other pollutants, including air toxics. 

The estimates are based primarily on county-level data and do not capture smaller-scale variability, such 

as living very near a retrofitted diesel source or regularly riding a retrofitted school bus. 

The results also do not include the impact of emission sources from Canada or Mexico. Results for 

border states will not reflect these potentially significant sources of transported emissions. 

The results are best used to assess the relative benefits among different locations or retrofit projects. 

 

For a complete discussion of the accuracy of these estimates, please see the chapter titled 

“Uncertainties, Limitations, and Quality Assurance” in the methodology document at 

www.epa.gov/cleandiesel/documents/420b10034.pdf. 

Outputs and Uses 

Question: What information does the Health Benefits Module provide? 
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Answer: This module provides information on health benefits from reduced exposure to diesel PM 2.5

emissions. 

The DEQ requires users to input detailed information regarding their retrofit projects. The DEQ then 

calculates the emission reductions for particulate matter (PM), nitrogen oxides (NOx), hydrocarbons 

(HC), carbon monoxide (CO), and carbon dioxide (CO2). 

The Health Benefits Module allows users to identify the counties where the emission reductions are 

taking place and to estimate the monetary impact of the resulting health benefits. These estimates are 

based on the change in fine particle concentrations and do not reflect changes in any other pollutants. 

Users can save and export files summarizing the emissions and health effects estimates. There is also a 

Health Benefits Methodology at www.epa.gov/cleandiesel/documents/420b10034.pdf that explains the 

methodology used to estimate the health benefits and the limitations of the estimates.

Question: How can this health benefits information be used? 

Answer: The Health Benefits Module is a helpful tool for preparing estimates and understanding benefits of 

specific emission diesel reduction projects. It can help in making informed decisions by comparing the 

benefits of several diesel retrofit options. It can also provide an estimate of benefits for EPA grant 

applications and help build public support for such projects. It should not be used in the calculation of 

emission reductions for State Implementation Plan (SIP) or conformity determination.

Cost Benefits (Explanation and Troubleshooting)

Question: Why does the Health Benefits Module use annual costs and benefits? 

Answer: Diesel retrofit projects tend to be capital-intensive in the first year due to the purchase and 

installation of new equipment or parts. The benefits, however, are spread out over many years as 

people continue to receive health benefits from the reduced emissions. 

In order to properly compare costs and benefits, this difference in timeframes must be addressed. We 

annualize the costs and the benefits so the user can tell at a glance if the benefits outweigh the costs on 

an annual basis. They also provide an indication of the scale and magnitude of the expected costs and 

benefits over the lifetime of the project.

Annualized costs are not the out-of-pocket costs in the first year, but what would be paid each year if 

the out-of-pocket costs were distributed the over the life of the engine. This is similar to the way a 

mortgage distributes the purchase price of a home over 30 years. If you used a loan to purchase the 

retrofit technology, the annualized costs are roughly what the loan payments might look like. 

Lifetime costs and benefits can be estimated by multiplying the annual costs or benefits by the number 

of remaining years in the life of the retrofitted vehicle. While the lifetime estimate does not take into 

account factors such as discount rates for benefits in future years or population growth, it does provide 

a rough estimate.

Question: Why are there no costs in the “Results” table of the Health Benefits Module? 

Answer: The Health Benefits Module estimates the annualized costs from the “install cost” (labor) and

“unit cost” (equipment) of the project, which are entered into DEQ’s Fleet Information screen under

“Add a New Technology.” If no cost information is entered, no cost information will appear in the 

benefits results table. 
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Please note, funding information can also be entered on the first screen of the DEQ by answering yes to 

“Do you want to estimate the total cost effectiveness of the project?” These are assumed to be total 

project costs, including overhead, and are not used to estimate annual costs. 

Question: I am trying to determine the health benefits for a marine engine repower project. While there 

are significant PM reductions, why do the benefits come up as $0?

Answer: The health benefits calculation depends on the PM reduction in tons. Sometimes, that reduction 

may be lower than you realize and the benefits may be so close to zero that they are accidentally 

truncated. Please download the Summary Results for both the DEQ calculation and the Health Benefits 

calculation in Excel or CSV and send it to cleandiesel@epa.gov 

Other

Question: Where can I get more information about particulate matter in diesel exhaust? 

Answer: For information about particulate matter, visit www.epa.gov/air/particlepollution 

Data Entry

Multiple Technologies

Question: Can I select combined emission control devices like DOC+CCV (Diesel Oxidation Catalyst + 

Closed Crankcase Ventilation) or DPF+CCV (Diesel Particulate Filter + Closed Crankcase Ventilation)? 

How about CCV by itself? 

Answer: CCV is included under “Emission Control Devices” as DOC+CCV, or DPF+CCV, but it is not listed as a 

stand-alone retrofit technology. To use CCV as a stand-alone technology, select “Other Emission Control 

Devices” from the “Technology” menu and enter the reduction percentages provided by the CCV 

manufacturer.

Question: Can I select multiple technologies such as engine repower with DOC or DPF? 

Answer: Some technologies cannot or should not be installed together (e.g. DPFs and Partial Flow filters). 

However, many technologies can be used at the same time. 

To add multiple technologies to a vehicle group, select the first technology and save it to the vehicle 

group. Then select the second, saving it to the same vehicle group. The screen always returns to the 

first vehicle group after adding a technology, so if there is more than one vehicle group, make sure the 

technology being added to the correct group. 

Fuel Types 

Question: The emission factors for NOx, PM, HC, and CO do not change when I select a different fuel 

type for my Vehicle Group. Why are these emissions not different for CNG and ULSD? 

Answer: Fuel type and volume are used to calculate only CO2 emissions. This is done by converting 

non-diesel fuel amounts to diesel-equivalent gallons, and then calculating CO2 emissions based on 

the diesel carbon content. 

Question: How does the DEQ estimate emission savings for switching from one fuel type to another? 

Answer: When you enter the vehicle information on the “New Vehicle Group” screen, select the fuel type 

being used before the retrofit. Then go to “Add a New Technology,” select “Fuel Options” and the fuel 

type that will be used after the retrofit. You can apply as many additional technologies as you need to. 
Page 14 of 21

Question: When I select CNG as the new fuel for my old diesel vehicle, all of the reduction percentages are 

zero. Why is this? 

Answer: The DEQ is primarily designed to calculate emission reductions for vehicles that use diesel fuel 

(ULSD, LSD, etc). All other fuels (biodiesel, CNG, LNG, etc) are converted by the DEQ to a diesel 

equivalent ("Calculated Fuel Volume") before any calculations are performed. Currently, the DEQ is not 

able to provide emission reductions for CNG and LNG fuel conversions because fuel-specific emission 

factors are not available in all cases. For more information, please visit the Alternative Fuel Conversion

website at www.epa.gov/otaq/consumer/fuels/altfuels/altfuels.htm

As a workaround for this, create two vehicle groups in the DEQ, one with a baseline engine using diesel 

fuel, and one with a baseline engine using the new fuel (you would need to know the annual amount of 

new fuel the used after the conversion, the annual of miles the vehicle would travel, and annual hours it 

would idle). Comparing the outputs for these two vehicles provides the CO2 emission reductions from 

the fuel conversion. 

Replacement

Question: Does the DEQ calculate emission reductions for engine replacements? 

Answer: Yes. Under “Technology Type,” select “Engine Replacement/Repower.” Then under “Technology” 

select “Engine Replacement.”

Question: Can the DEQ be used to calculate emission reductions from replacing a diesel engine with 

electric technology? 

Answer: Installing electric technology reduces diesel emissions to zero. To quantify the reductions, start by 

entering the fleet information. For ”Technology Type,” select “Emission Control Devices,” and for 

“Technology, ” select “Other Emissions Control Devices.” In the “Reduction by Pollutant” box, enter 

100% for each of the pollutants. The DEQ will quantify the project’s emission reductions using 

reductions of 100 percent. 

Question: For engine repower or replacement projects, should "engine replacement/repower" be selected 

as the technology or should the DEQ be run twice, first with the baseline engine and then with the new 

engine?

Answer: Please select "engine replacement/repower" as a technology. 

Truck Stop Electrification

Question: How are emission reductions determined for Truck Stop Electrification (TSE)? 

Answer: The DEQ calculates TSE emission reductions the same way it does for other idle reduction 

technologies. The best calculations will result from inputting your best estimates of the number and 

type of trucks that would use the TSE facility, as well as the expected reduction in idle hours. 

Trailer Refrigeration Unit

Question: How can I calculate the emissions reduced by replacing a trailer refrigeration unit (TRU) in a box 

trailer?

Answer: TRUs are not currently a technology option in the DEQ. As a workaround, create a Vehicle Group 

for the TRU by selecting "Non Road", "Stationary" and "Power Generation". Then select "Engine 

Replacement" as the technology. Be sure that all Vehicle Group inputs (model year, hp, usage rate, fuel 

usage, etc) are for the TRU and not for the tractor-trailer. 
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Uncertainty, Missing Information, Averaging, and Diverse Fleets

Question: We have a project with a variety of fleet components, but we are unsure of the exact vehicles 

that will be in the program. What should we use for the DEQ calculations?

Answer: If you are unsure of the exact fleet, you should use your best judgment and any past history you 

have with such a program to make estimates in the DEQ. 

Question: What if I don’t have all of the information required to use the DEQ? 

Answer: The DEQ will self-populate some default values when you select “Get Default Values.” Other

defaults must be input manually. They can be found in the DEQ Default Values document at 

www.epa.gov/cleandiesel/documents/420b10035.pdf. You can also make your own estimates; 

however, using real-life data is highly recommended. 

Question: For nonroad vehicles, the DOC unit cost varies depending on engine size. Can we average the 

costs per unit or must we do a separate run for each application? 

Answer: You can either do separate runs for each unit or average them, but the separate runs will give you 

more precise results. 

Question: How do you estimate emissions for a fleet with multiple, diverse vehicles? Must a separate 

calculation be performed for each vehicle? 

Answer: You may generate a report for each vehicle or group of similar vehicles. Alternately, you may run a 

single report using “average” inputs to minimize the number of runs. Separate runs will give you more 

precise results. For more information on the best ways to group vehicles and still ensure accuracy, refer 

to the Appendix of this document. 

Question: How do I handle a project with both on-road and nonroad vehicles? 

Answer: The DEQ can support multiple Vehicle Groups, including a mix of on-highway and nonroad in the 

same Fleet. Include the on-road/highway vehicles in one vehicle group and the nonroad in another.

Fleets

Question: Which inputs are for a single vehicle and which are for the entire fleet? 

Answer: All of the inputs except for Fuel Volume should be entered for per vehicle or engine. Fuel Volume 

should be entered as a total for the entire Vehicle Group. 

Baseline Emissions

Question: How can I calculate baseline emissions using the DEQ?

Answer: To calculate baseline emissions, begin by entering the information about your fleet. When you 

”Add a New Technology,” select “Emission Control Devices” for “Technology Type” and “Other Emission 

Control Devices” for “Technology.” This will default the reduction percentages to zero and the DEQ will 

calculate only the baseline emissions. Please note, if you do not add any technology to your fleet, the 

DEQ will calculate baseline emissions and display them on the Emission Results Screen, but the results 

won’t appear on the DEQ Summary Results spreadsheet. 

Question: For engines with OEM catalysts, adding a new retrofit device sometimes requires the removal of 

the original catalyst. How does the DEQ take the removal of the catalyst into consideration when 

calculating emission reductions? 

Answer: The DEQ’s baseline emission factors are always based on certified engine configurations, which 

include OEM catalysts. Whether a retrofit device is added to a vehicle with an OEM catalyst or to a 
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vehicle that has had the catalyst removed to accommodate a new device, the DEQ calculates emission 

reductions from the certified OEM baseline. Please keep in mind that project can only claim emission 

reductions from a vehicle/engine’s certified baseline.

Idle Reduction

Question: Are idling hours included in the nonroad “Usage Rate”? 

Answer: Idling hours are included in the default “Usage Rate” for nonroad vehicles. If you are entering 

actual “Usage Rate” hours, be sure to include idling hours. 

Question: The idle reduction technologies display emission reductions for NOx, PM, and CO2 only. What 

about HC and CO? 

Answer: Although idle reduction technologies may reduce HC and CO emissions, idling emission factors are 

available only for NOx, PM, and CO2 and only for on-highway vehicles. 

Question: When calculating emission reductions for idle reduction technology, the reduction percentages 

that populate the input screen are not the same as those shown on the downloaded spreadsheet. Why? 

Answer: For on-highway vehicle calculations, the DEQ uses two sets of emission factors, idle emissions and 

running emissions. When a user applies an idle reduction technology, the reduction percentages that 

populate the input screen reflect only the idle emissions. The downloaded spreadsheet shows the 

reduction percentages for both idling and running emissions. For instance, an idle reduction technology 

may reduce a vehicle’s idle emissions by 90%, but it may reduce the vehicle’s overall emissions by only 

10%. This will vary based on the vehicle idling hours relative total usage hours. 

Maintenance and Operating Costs

Question: How can I include project maintenance and operating costs in the DEQ estimates? 

Answer: These costs do not have specific input fields in the DEQ. They may be included as part of the total 

project costs. Enter them as part of the total funding on the first screen by answering “yes” to the 

question “Do you want to estimate the total cost-effectiveness of the project?”. 

Vehicle Definitions and Classes

Question: How does the DEQ define a bus? Does it include hotel or airport shuttles?

Answer: The DEQ calculates emission for only medium heavy-duty and heavy heavy-duty vehicles 

(Classes 5-8). This includes school buses and transit buses. Shuttle buses are usually Class 4 or 5, but 

please verify this is the case for your specific fleet. For a more information on vehicles and weight 

classes, please see the DEQ Default Values document at 

epa.gov/cleandiesel/documents/420b10035.pdf. 

Question: Where can I find the definition of the different vehicle classes? Are they the same as DOT classes? 

Answer: For highway vehicles, medium heavy-duty and heavy heavy-duty vehicles are included in the DEQ. 

The classes are defined by US DOT by gross vehicle weight rating (GVWR). 

• Class 5; 16,001 - 19,500 lbs GVWR

• Class 6; 19,501 - 26,000 lbs GVWR

• Class 7; 26,001 - 33,000 lbs GVWR

• Class 8a; 33,001 - 60,000 lbs GVWR

• Class 8b; 60,001 lbs GVWR and over
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For further definitions of vehicles and weight classes, please see the DEQ Default Values document at 

epa.gov/cleandiesel/documents/420b10035.pdf. 

Verification Information

Question: Does EPA have a list of engine family names that have been approved for verified products? 

Answer: No. Unlike CARB, EPA does not issue a list of engine family names for each technology that 

has been verified. Please refer to the Verified Technology Listing at 

www.epa.gov/cleandiesel/verification/verif-list.htm#retrofit for specific engine model

applicability and general operating criteria. Engine certification data, including engine family 

names, are available at www.epa.gov/otaq/certdata.htm#largeng

Input Errors

Vehicle Groups

Question: I get the following error message when I try to add a vehicle group to a saved fleet: “An 

Unexpected Error has Occurred. We are sorry, the Diesel Emissions Quantifier has experienced an 

unexpected error. The details of this error have been logged and the development team has been 

notified. If you left your browser inactive for over 30 minutes, this error is due to your session timing 

out.” What should I do?

Answer: If possible, take a screenshot of the error page and send an email to cleandiesel@epa.gov, with 

“Could not Update Saved Fleet” in the subject line. Also include as much info as you can about the 

inputs you entered, info about the vehicle group, etc, as well as your DEQ user email. Meanwhile, try 

logging out, closing the browser and then logging back in again. You can also try running the DEQ

without signing. 

Question: Is there a limit to how many Vehicle Groups can be included in one Fleet? I have entered 47 

Vehicle Groups and when I try to quantify emissions, I get an error message saying the DEQ is 

experiencing an error.

Answer: We recommend that you keep the number of Vehicle Groups under 30. 

Model Year

Question: Sometimes the DEQ does not allow me to select a specific model year for my vehicles. 

Answer: Depending on the vehicle type, the DEQ may assume that only certain model years are able to be

retrofitted. If the model year of your vehicle is not displayed as an option, select the closest model year

that is available. 

Horsepower

Question: The DEQ does not list the horsepower of my nonroad vehicle. The nearest available horsepower 

option is either too high or too low. What should I do?

Answer: We recommend using the closest available horsepower option. At this time, the DEQ does not have 

data for every available horsepower, as data collection and approval of emission factors may take years. 

Replacement (Engine and Vehicle)

Question: How do I calculate emission reductions for vehicle replacement using the DEQ? 

Answer: The DEQ does not offer an option for vehicle replacement. To calculate emission reductions for a 

vehicle replacement project, please select “Engine Replacement” for “Technology Type”. 
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Technologies

Question: If idle reduction is not an option for nonroad equipment, how can I quantify emission reductions 

for automatic shutdown devices on nonroad vehicles? 

Answer: At this time the DEQ does not support idling strategies in nonroad engines. Please consider using

another calculation method. 

Question: When using the DEQ, only technologies that have been verified are listed. How can I include an

Emerging Technology in the calculations? 

Answer: Please refer to the Emerging Technology List at www.epa.gov/cleandiesel/verification/emerglist.htm and manually input the projected emission reductions for PM NOx, HC and CO. 

Question: The emission reduction results for several technologies I’m using, such as direct fired heaters, are

0%. What might be the problem?

Answer: If the “Idle Hours Reduced” was left blank, then you will get 0% reductions. Be sure to enter the

number of idle hours in this field. 

Fuels

Question: How do I calculate emissions reductions if the fuel blends we are using, like high blends of 

Biodiesel plus ULSD, are not listed? 

Answer: The DEQ results are estimates, so please select the option that is closest to your real-world 

situation. 

Question: The DEQ has selections for B-20 and B-100 but nothing in between. The National Clean Diesel RPF

indicates that any blend of Biodiesel (B-5 to B100) is eligible. How do I calculations on something other 

than B20 and B100? 

Answer: The DEQ can’t accommodate blends other than B20 and B100 at this time. You may select the 

option that is closest to the fuel you are using or use another calculation tool more geared to fuels. 

Question: My organization has 20 trucks and we’ll be replacing the engines in 10 of them. For the “Fuel 

Volume” for the fleet, do we enter the total fuel consumed by the 20 trucks in the fleet or just the 10 

that are going to be replaced? 

Answer: Create a Vehicle Group of 20 vehicles, then select “Engine Replacement” and apply it to 10 of the 

20 vehicles. For “Fuel Volume”, enter the combined fuel consumption for the entire Vehicle Group (all 

20 trucks).

Currently Documented Errors

The DEQ is an estimation tool only and users may not be able to quantify all possible scenarios. EPA suggests 

you familiarize yourself with the options. These are outlined in 

• Health Benefits Methodology www.epa.gov/cleandiesel/documents/420b10034.pdf 

• Current Methodologies in Preparing Mobile Source Port-Related Emission Inventories

www.epa.gov/cleandiesel/publications.htm#ports. 

If the DEQ is not a good fit for your project, you may want to download the emission factors from

www.epa.gov/otaq/nmim.htm and make your own calculations. You can also use other available data 
Page 19 of 21

sources. If you are using the DEQ for a DERA application, you can use any documented methodology to 

calculate emission reductions as long as you cite the source in the application. 

Below are some common errors and suggested work-around solutions. If the problem you are encountering 

is not listed, please log out, restart the DEQ, and try again. If the error occurs again, please send your inputs 

and error message (screen shot or copied and pasted) to cleandiesel@epa.gov. 

Problem: I can’t log in to my user account.

Solution: Send an email to cleandiesel@epa.gov with the subject line “User Account Problem” and include 

your log-in email. Meanwhile, you can create a new user account using a different email address. 

Problem: My previously saved scenarios are not working. 

Solution: Due to updates to the DEQ structure, some saved scenarios may no longer work properly. If you 

encounter this, please delete the old Fleets and recreate them. In some cases, users are able to access a 

saved Vehicle Group, but are not able to quantify it. This can be fixed by deleting the existing 

technology, re-entering it, and then clicking on “Quantify Emissions.” 

Problem: I can’t find Total Cost-Effectiveness on the exported Results spreadsheets.

Solution: Total Cost-Effectiveness is displayed on the Summary Results screen, but it is not yet available on 

the spreadsheets. Please refer to the screen directly after clicking "Quantify Emissions,” or calculate 

yourself:

• The DEQ calculates Total Cost-Effectiveness by taking the total project funding and dividing it by the 

total Lifetime Tons Reduced of each pollutant. 

• The DEQ calculates Capital Cost-Effectiveness by taking the total Unit Cost and Installation Cost for each 

technology added and dividing that by the Lifetime Tons Reduced for each pollutant.

Problem: The Lifetime Emissions equal the Annual Emissions.

Solution: Based on our modeling, the DEQ uses standard lifetimes for vehicles and non-road equipment, 

even though they may be used longer. The DEQ assumes if a vehicle is older than its standard life, its 

remaining life is just one year, resulting in Lifetime Emissions equaling Annual Emissions. One workaround is to multiply the Annual Emissions by your estimate of the vehicle’s remaining life.
Page 20 of 21

Appendix: Grouping Vehicles for Calculations in the DEQ

The DEQ is designed to provide emission reduction estimates for a variety of fleet and technology options. If 

your project has a mix of vehicle and engine types, you do not have to run the DEQ for each vehicle. You can 

divide the fleet into several groups and run the DEQ several times. The following guidelines are based on the 

on-road and nonroad emission standards. For more information, see 

• On-Highway Heavy Duty Compression Ignition Exhaust Certification Emission Standards

www.epa.gov/otaq/standards/heavy-duty/hdci-exhaust.htm

• Non Road Compression Ignition Exhaust Emission Standards

www.epa.gov/otaq/standards/nonroad/nonroadci.htm

1) First, separate the DEQ Calculation Groups for multi-sector projects into Highway/On-road, Nonroad, and 

Marine. Marine retrofits require a separate DEQ run for each vessel, so the following will apply only to 

Highway/On-road and Nonroad vehicles. 

a) On Highway. 

i) First, group all on-highway vehicles into their respective Target Fleets: 

(1) City/County Vehicle

(2) Delivery Truck

(3) School Bus

(4) Transit Bus

(5) Refuse Hauler

(6) Emergency Vehicle

(7) Long Haul 

(8) Short Haul

ii) Within each Target Fleet, group vehicles based on the Class/Equipment: 

(1) School Buses

(2) Transit Busses

(3) Class 5

(4) Class 6

(5) Class 7

(6) Class 8a

(7) Class 8b

iii) Next, divide the Class/Equipment groups by the following Model Year ranges (based on the OnHighway PM level emission standards ) : 

(1) Pre-1987 

(2) 1988-1990

(3) 1991-1993

(4) 1994-1997

(5) 1998-2003

(6) 2004-2006

(7) 2007-2010
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iv) Finally, within each Model Year group, divide your vehicles based on the type of retrofit technology 

that will be applied (i.e. Diesel Oxidation Catalyst + CCV, Engine Replacement, etc)

b) Nonroad (non-marine vessels/engines) 

i) First, group all nonroad vehicles into their respective Target Fleets: 

(1) Agriculture

(2) Construction

(3) Ports and Airports

(4) Rail

(5) Stationary

ii) Within each Target Fleet, divide the vehicles based on the Class/Equipment (too many to list here, 

and realize that some nonroad equipments can overlap so you could have fewer groups than you 

realize). 

iii) Within each Class/Equipment group, divide by the following Horsepower/Model Year combinations

(based on nonroad emission standards for NOx, PM, NMHC+NOx and CO): 

(a) <11 hp and pre-2000 (Tier 0) 

(b) <11 hp and 2000-2004 (Tier 1) 

(c) <11 hp and 2005-2010 (Tier 2)

(d) 11≤ hp <25 and pre-2000

(e) 11≤ hp <25 and 2000-2010

(f) 25≤ hp <50 and pre-1999

(g) 25≤ hp <50 and 1999-2003

(h) 25≤ hp <50 and 2004-2010

(i) 50≤ hp < 100 and pre-2004

(j) 50≤ hp < 100 and 2004-2010

(k) 100≤ hp < 174 and pre-2003

(l) 100≤ hp < 174 and 2003-2010

(m) 174≤ hp < 301 and pre-1996

(n) 174≤ hp < 301 and 1996-2002

(o) 174≤ hp < 301 and 2003-2010

(p) 301≤ hp < 603 and pre-1996

(q) 301≤ hp < 603 and 1996-2000

(r) 301≤ hp < 603 and 2001-2010

(s) 603≤ hp < 750 and pre-1996

(t) 603≤ hp < 750 and 1996-2001

(u) 603≤ hp < 750 and 2002-2010

(v) > 750 hp and pre-2000

(w) > 750 hp and 2001-2010

iv) Finally, within each Horsepower/Model Year group, divide your vehicles based on the type of 

retrofit technology that will be applied (i.e. Engine Replacement, Engine repower, Hybrid 

Replacement, etc.)