Even though I may not agree with everything in the FAQ’s below I believe NGV answers many questions that would-be CNG Converters are asking.
Q Why are people converting their vehicles?
A The rising cost of gasoline is prompting many people to investigate options to
retrofit or convert their car or pick-up truck to run either (1) solely on natural gas,
which is referred to as “dedicated” or (2) to run on gasoline or natural gas, which the
federal government refers to as “dual-fuel” although the accepted nomenclature for
such vehicles is “bi-fuel.”
Q What about heavy-duty trucks?
AThis document does not address conversion of heavy-duty vehicles over 14,000 pounds, such as buses, many shuttles and/or work trucks. In general, very few systems have been approved for converting vehicles over 14,000 pounds. However, there is a great deal of interest in the industry in going after heavy-duty conversions, so we expect more systems to be available for such vehicles in the future. In addition, new OEM vehicles can be purchased with engines designed to run on natural gas. The federal government’s current guidance on the use of aftermarket conversion systems is available at
Q How much does it cost to convert a vehicle?
A Converting a new vehicle provides the greatest opportunity to save fuel cost
and, thereby, pay back the conversion cost and generate life-cycle savings. The costs
range from $12,000-$18,000 depending on the size of the vehicle and include the
retrofit system, fuel tanks and related tubing/brackets, and the installation. The
amount of fuel capacity requested by the customer significantly impacts cost.
Potential customers should contact manufacturers directly about vehicle conversion
costs, but the following are general “ballpark” estimates of retail light-duty vehicle
conversion costs provided by manufacturers.
Q What impact will converting my vehicle have on the original warranty?
A Generally, installing aftermarket parts does not affect the original equipment
manufacturer’s warranty. This is the case with the installation of aftermarket
conversion systems. EPA has stated that the “vehicle’s original manufacturer remains
Fact sheet: Converting lightduty vehicles to natural gas liable for warranty of any systems which retain their original purpose following conversion, except in cases where the failure of such a system is determined to be caused by the conversion.” In addition, EPA guidance states that “the conversion system manufacturers would be responsible for the emissions warranty for any parts or systems added by the conversion.” For more information on warranty provisions, the parts covered, and the duration of these warranties, see EPA guidance here —
Q What federal or state tax credits apply to conversions?
A The federal income tax credit for dedicated NGVs expired in 2010, but several
states provide incentives to convert vehicles to run on natural gas. These tax credits
are state-specific and some are temporary. For a list of state programs, see
http://www.ngvamerica.org/incentives/stateNGV.html or check with your
appropriate state taxation office concerning state tax credits.
Q Where can I refuel my CNG Vehicle?
A Before you convert your vehicle to run on natural gas – or purchase a used
CNG vehicle — be sure to investigate your fueling options. While there are about
1,000 CNG fueling locations in the U.S. (and the list is growing), only about half are
open to the public. Others allow public refueling only after an account has been
established (referred to as limited public access), while still others allow public fueling
with convenient credit card and/or proprietary billing card access (referred to as full
Q Where can I find a list of CNG fueling stations?
A The most comprehensive lists of CNG stations are available from the following
(U.S. DOE- maintained site of U.S. stations)
(WestStart/CALSTART- maintained web site for California, Nevada and Arizona.
Q What if I am planning a long trip?
A Generally, CNG vehicles are best suited to applications where the vehicle
remains in one area to allow for regular refueling at existing fueling sites. While fueling
networks are developing in many markets, there are gaps between markets that may
make long-distance travel more challenging. Use the above websites, then contact the
station(s) you plan to use on your trip to confirm the information is up to date.
Q My home is heated with natural gas. Can I tap into my home system to
fuel my vehicle?
A. Yes. Homeowners with an existing natural gas supply line may be able to
purchase a home refueling system designed to fill their vehicle overnight. Gas from
the same supply line that feeds their house is compressed and stored onboard the
vehicle by a “vehicle fueling appliance”. Some of these devices are about the size of
an outdoor house air-conditioning unit and the unit is installed outdoors, usually
adjacent to your garage. There also is a unit called the Phill that is smaller and can be
installed in the garage. The larger (outdoor) vehicle refueling appliances compress and
dispense about 0.9 gasoline-gallon-equivalent per hour. The Phill compresses and
dispenses about 0.4 gasoline-gallon-equivalent per hour. See
http://www.impco.ws/fuelmaker.asp for more information.
Q Are there tax credits for installing home CNG refueling systems?
A Home CNG refueling devices qualify for a federal tax incentive up to $1,000
and may qualify for additional state tax incentives or grant subsidies. Some states also
have tax credits for home refueling. More information about the available federal tax
incentive can be found at http://www.ngvamerica.org/incentives/index.html
Q How would you describe the certification requirements for aftermarket
A Both the federal Environmental Protection Agency (EPA) and the California
Air Resources Board (CARB) require the manufacturers of aftermarket systems to
certify that their conversion systems meet emissions and onboard vehicle diagnostics
interface requirements. EPA and CARB can levy substantial fines for violating this
requirement, since it is against the law to tamper with emissions systems. The only
way to protect against a tampering violation is to have valid certificate of conformity
from EPA or a CARB Executive Order for the conversion system. (See below for
vehicles that are pre-2003 model year and/or beyond their “useful life.”)
Q How does the EPA have this authority?
A The EPA has the authority under the Clean Air Act to regulate vehicle
emissions for all new motor vehicles. Moreover, it also has authority to regulate
modifications of in-use vehicles if the modification tampers with the vehicles emission
control systems. For a history of EPA’s regulatory authority, see
Q How does the law work in California?
A Federal law authorizes California to carry out and enforce its own more
stringent vehicle emissions regulations for vehicles sold or registered in California.
These California-specific requirements are promulgated by the state’s Air Resources
Q Are any other states given the same authority?
A Under federal law, other states are permitted to adopt California’s emissions
regulations for new vehicles. States adopting – or phasing in adoption of – the
California new vehicle standards include: Arizona, Colorado, Connecticut, Florida,
Maine, Massachusetts, Maryland, New Jersey, New Mexico, New York, Oregon,
Pennsylvania, Rhode Island, Utah, Vermont and Washington. EPA has indicated that
– unless these states have specifically adopted California’s aftermarket regulations or
implemented similarly restrictive rules – used vehicles operated in these states may be
legally retrofitted using EPA-certified systems. Vehicle owners and qualified retrofit
system installers should check with their own state motor vehicle and/or air quality
agencies to determine the definitions of new and used vehicles and what other engine
retrofit systems guidelines apply.
Q How many companies are offering certified systems?
A The number of Small Volume Original Equipment Manufacturers (SVM)
continues to increase as new companies with automotive engineering expertise see the
aftermarket retrofit opportunity. Currently, there are nearly a dozen manufacturers
offering EPA-certified systems for about a dozen GM and Ford light-duty “engine
families” covering about 40 vehicle models (and various iterations of the same base
models). These include the GM 3.5L, 3.9L, 4.8L, 5.3L, and 6.0L engines and the Ford
2.0L, 2.3L, 4.6L, 5.4L, 6.2L and 6.8L engines. Note: Not all vehicles with these
engines are covered in the engine test groups for which certifications have been
granted. In addition, there are no certified natural gas engine conversion systems
available in the U.S. for any other light-duty vehicle brands.
Q Where can I find a list of manufacturers?
A Visit http://www.ngvamerica.org/pdfs/marketplace/MP.Analyses.NGVsa.
pdf for an up-to-date list of EPA- and CARB-certified engines retrofit and repower
Q How do retrofit system manufacturing companies get engines certified?
A To obtain an EPA Certificate or a CARB Executive Order, the retrofit system
manufacturer must submit substantial emissions performance data and related
documentation for each engine family for review. Additionally, new converters may
be asked to submit a converted vehicle for rigorous testing to verify this data.
Q Why is this testing required?
A This testing ensures that the retrofitted vehicle meets the same stringent
emissions requirements as original equipment vehicles. The testing also ensures that
the retrofit system works seamlessly with the on-board diagnostics system to warn the driver when emissions are outside of approved parameters and to log those anomalies in the computer memory for downloading by the automotive service technician. This is an important criterion, since systems that do not do this will fail state and local emissions tests.
Q How expensive is it to comply with these requirements?
A The process of engineering, manufacturing, installing, pre-testing and then
submitting a proposed retrofit system to an EPA- or CARB-approved laboratory for
certification is a time-consuming and expensive process that may cost as much as
$200,000 or more per engine family.
Q How long does this certification last?
A EPA certification applies only to the installation of that system for a limited
time period, usually no longer than December 31 of the year following the year the
certificate was granted. Manufacturers may opt to ‘carry-over” their certifications into
future years by filing additional documentation and paying a fee, thus allowing them
to convert a previous model-year vehicle (for which they obtained certification) in
later years. However, Executive Orders issued by the California Air Resources Board
for a particular vehicle model year and test group do not expire.
Q Are used natural gas vehicles available for sale?
A Government agencies have been the largest purchasers of light-duty natural gas
vehicles, and many sell their vehicles after reaching a specific age or mileage
benchmark. Examples include federal, state and local government agencies, airport
and transit authorities (light-duty sedans and pick-up trucks are often used by security,
route supervisors and/or maintenance personnel). While these vehicles do not qualify
for the vehicle purchase tax credit because they were already placed in service, they
are often low-cost and have remaining life on them. The federal government (GSA)
site for auctions is: http://autoauctions.gsa.gov/autoauctions/home.seam
Q What about retrofitting older vehicles?
A The U.S. EPA has indicated that its certification procedures are appropriate for
vehicles that are within their useful life, which is roughly defined as 10 years or
120,000 miles, although the exact definition of useful life has changed over time. The
EPA is expected to issue future guidance on this issue. In addition, manufacturers
generally do not maintain active certifications for vehicles with high (or even medium)
mileage due to technical complications caused by long-term operation on gasoline.
For any pre-2000 vehicles or any vehicle with mileage exceeding the useful life
definition for that model and model-year, EPA guidance appears to indicate that
certification is not required, although the manufacturer must have a reasonable basis
to believe that the system will not increase emissions. For 2000 to 2003 vehicles that
have not yet reached 120,000, EPA guidelines indicate that certification of the retrofit
system is required, which does not make this option economically attractive. See
EPA’s web site for further clarification on this issue including guidance on converting
vehicles older than 10 years or beyond 100,000 – 120,000 miles.
Q What if a system is certified in another country?
A To meet the U.S. requirements, a system must be certified by either the U.S.
EPA or the State of California. The fact that a system is certified or approved in
another country is irrelevant. These systems also are not eligible for the federal
income tax credit.
Q Are aftermarket installers certified?
A Neither the federal government nor California require the businesses or
individuals who install aftermarket conversion systems to be certified or licensed to
do conversions. Because of the liability for in-use emissions and safety,
manufacturers of EPA- or California-certified conversion systems train companies,
often referred to as qualified system retrofitters, to install their systems, and typically
they do not sell their system to untrained or unapproved installers. In addition, some
states, including Oklahoma, have established state retrofit system installer training and
Q Can I install this system myself?
A Installation by a non-qualified installer could damage the retrofit equipment or
the engine, compromise vehicle performance, or render the vehicle unsafe to operate.
Q Are there other safety considerations?
A The installer is responsible for obtaining the fuel storage system components
(cylinders, high-pressure tubing, press release device, brackets, protective plates) and
for installing them in accordance with the National Fire Protection Association’s
Vehicular Fuel System Code (NFPA 52). These safety-oriented issues are the domain
of the local fire marshal, and most jurisdictions have adopted NFPA 52 as their
standard for proper installation of natural gas vehicle systems. Consumers should ask
installers to confirm that the installation meets NFPA 52 requirements.
Q How can I find the names of the qualified system retrofitters?
A They are available from the individual manufacturers.
Q What about routine maintenance?
A Because natural gas engines work essentially the same way as gasoline engines –
an air-fuel mixture is injected into the intake manifold, drawn into the combustion
chamber, and then ignited by a sparkplug – most engine service issues are very similar
and can be handled by a dealer or automotive shop. If there is a retrofit issue, such
as a faulty injector or loose compression fittings, these would be taken care of by the
installer. Occasional inspection of all vehicle systems is generally good practice,
regardless of fuel type. See below for safety inspection requirements.
Q What safety requirements apply to natural gas cylinders?
A The National Highway Traffic Safety Administration, the federal agency with
jurisdiction over vehicle safety, requires that all CNG fuel storage cylinders conform
to federal safety standards found in FMVSS 304 (49 CFR 571.304). Natural gas
cylinders also must have a label that (1) states the date of manufacture and the date
that the cylinder is required to be removed from service (typically 15-20 years), and (2) instructs the vehicle owner/operator to have a qualified visual inspection of the tankevery 36,000 miles or every 3 years (whichever occurs first) and/or after an accident or fire. Inspections are performed to look for tank and bracket damage (e.g. gouges, cuts, abrasions, dents, corrosion, rust, general wear, etc). Converters and vehicle owners should have documentation that this safety inspection has been done,
especially if installing used cylinders that still have remaining life (as noted on the
cylinder manufacturing label).
Q Where do I find a qualified cylinder inspector?
A Qualified cylinder inspectors are located throughout the US and Canada. The
cost/time associated with a cylinder inspection is minimal. More information about
CNG cylinder inspections and links to certified inspectors is available at
http://www.cleanvehicle.org/technology/cylinder.shtml Check with the
manufacturer or the qualified system retrofitter concerning recommended service
practices and warranty coverage.
If your general question was not answered by this document, please contact us at
Disclaimer: These questions and answers are provided for informational purposes
only. If legal advice or other expert assistance is needed, the services of competent
professional should be sought.
I hope these help to answer some of your questions, Jim
Jim Younkin is a mechanic with more than thirty years experience in automotive repair. His passions include car racing, mountain climbing, ice climbing, and CNG conversions. He enjoys sharing his passions and connecting with others of like mind. See more about Jim at http://www.younkincng.com
email: firstname.lastname@example.org or 801-427-2284