What size station do I need?

You must first Determine the amount of CNG fuel required daily for your CNG Fleet. For example
a typical CNG school bus covers 80 miles per day, gets 4 miles per gallon and is parked at night
for up to 12 hours or more. Assuming you have 6 CNG school buses in your fleet you will require
120 GGE per night. (80 miles, divided by 4 mpg = 20 GGE per bus, times 6 buses = 120 GGE
total.) Since you have 12 hours to accomplish fueling your system can be a time-fill type system
and the compressor can be sized based upon your need of 120 gallons over a 12 hour period.  

How does CNG fueling work?

The primary components of a CNG station are, one or more gas compressors, a Gas dryer, time-
fill fueling post assemblies, and might include a series of CNG fuel storage tanks and or a fast-fill
island type dispenser with a credit card reader to activate fueling. The compressors take low line
pressure gas from the main gas pipeline, compresses it to high pressure and dispense it into
CNG vehicles via time-fill or fast-fill fueling methods.  

What is the difference between Fast-Fill - Time-Fill, why would I choose one over the

If all or most of your CNG vehicles return to a central location overnight or during the day, for a
period of hours, Time-Fill is the most efficient and economical means of fueling. In a Time-Fill
configuration the vehicles can be parked in their assigned fueling space, connected the hose
and the vehicles will slowly fuel overtime. Fueling typically begins automatically when the first
vehicles is connected and will shut off automatically when the last vehicle is full. No attendant is

In a Fast-Fill configuration the CNG compressor takes the low line pressure gas and
compresses it up to 5000 psi into appropriately rated CNG storage vessels. CNG vehicles then
pull up to CNG Fast-Fill dispenser which resembles an ordinary liquid fuel dispenser like you see
at a gasoline station. Fast-Fill CNG fueling requires about the same amount of time as fueling
with any conventional fuel. Most Fast-Fill CNG systems incorporate a card reader for
authorizing, dispensing and billing the transaction.  

What is the cost of a gallon CNG ?

This depends upon where it is purchased. Some are owned by private fueling companies others
by various governmental agencies.

Are there any grants or incentives for installing CNG fueling stations ?

Yes! There are many different Grant funds from Federal and Local Government for this purpose
and the amount you may be eligible for depends upon a number of criteria. Our suggestion is to
contact your local Clean Cities Organization or Department of Energy to obtain related Grant
information for your CNG fueling needs and determine your eligibility for those funds or contact
us directly.

How do I get started ?

AFSC would be pleased to visit with you and determine the best size and type of CNG fueling
equipment for your needs, walk the site with you to provide ideas about the best location for the
equipment and the budgeting estimate for the station equipment and construction. AFSC can
also help or advice with the NFPA codes.



Access is provided only to owner’s vehicle (s). Typically, fueling equipment is located at central
fleet depot, often in secure area and/or requiring access code or key to activate dispensing
equipment. No other private or public accounts have access. Examples: utility, transit and
government public work depots where public fueling is not allow.


    LIMITED PUBLIC ACCESS: Access to fueling capability is limited by physical barrier, e.g.
    the dispenser is located in secure area open during limited hours of operation and/or
    requiring pre-approved access key or gate code, or by administrative requirement, e.g.,
    dispenser requires pre-approved fuel card or billing code to activate. Generally, transient
    customers are prohibited and cash and/or credit card sales are not available. Examples:
    utility or government public works fleet yards where a limited number 0f pre-approved
    “guest” fleets are authorized to use “host” fueling site.
    FULL PUBLIC ACCESS: Comparable to using a traditional retail gasoline or diesel
    station, site access is unencumbered and fueling capability is open to all via use of
    proprietary fueling cards, major credit cards and/or cash (if station is manned) Examples
    include dedicated public retail natural gas station. CNG dispensers  located at traditional
    petroleum locations, and CNG dispensers installed adjacent to typically private-access-
    only fleet yards (e.g., at transit agency or government public works depot that agrees to
    provide public access “outside the fence”).

How much does a typical CNG fuel station cost ?

There is no "typical" CNG fuel station, because the costs depend essentially upon 3 things.
    [1] Time Fill vs. Fast Fill will made the biggest difference on cost..
    [2] The amount of fuel required over what period of time?
    [3] The site of conditions where the station is to be constructed.  


A CNG station’s fueling equipment needs and costs will be based on compression, storage,
dispensing, fuel-metering/management and redundancy requirements. Available utility services
also impact station design, equipment selection and operation strategy.

    COMPRESSORS.– Compressor sizing and cost factors include: total fuel throughput and
    peak flow needs, inlet gas pressure and its impact on horsepower requirements to
    achieve the desired flow rates; the need for-and amount of-redundancy required and how
    this may affect compressor(s) sizing; electric drive vs. natural gas engine-drive;
    incremental cost per added scfm; type of sophistication of the controller and remote

    GAS DRYERS.-   Dryer sizing and cost factors include: volume and flow rates of fuel to be
    processed; inlet gas pressure and moisture content; and automated or manual
    regeneration capability.

    STORAGE.– Factors affecting storage equipment sizing and cost include: whether any
    storage is needed; the type of system (e.g., buffer versus cascade); amount and pressure
    of total storage needed to help meet peak demand periods; type of storage container
    selected (ASME, DOT, etc); and controls.

    NUMBER AND TYPE OF DISPENSERS.– Factors to consider include whether to use time-
    fill posts, fast-fill dispensers or both; the pressure, flow rate and type of nozzle(s); and
    number of filling dispensers needed.

    Factors affecting equipment selection and cost include: whether a card reader system is
    necessary; the sophistication of the card reader system; and modem system.
TIME FILL: Fueling is accomplished over an extended period of time, typically overnight or during lulls in daily operation hours,
using time fill posts. Gas is compressed and gradually delivered directly to vehicle fuel cylinders. No significant (if any) on site
fuel storage is included and there’s no fast filling capacity. Because of the need to park vehicles for extended periods of time,
this type of fueling capability is most common to fleet owner operator sites such as utility yards, school bus depots and
government public works yards. However, there are still cases where utilities own and maintain this station on their customers’
sites for their customers’ use.
FAST FILL: Fueling is accomplished in relatively the same time as liquid fuels. Gas is compressed and stored in on site fuel
storage containers at elevated pressures (typically 4500—5000 psi), from which CNG is transferred to the vehicle fuel cylinders
through fast fill dispensers. This type of fueling capability is used anywhere vehicles need to fill quickly, including all public
access sites and many private access locations where time fill fueling capabilities does not meet the operational needs.
COMBINATION FILL: This type of station includes both time fill and fast fill dispensing capability. These type of stations are
often found on fleet owner operator sites where mid-day fueling capability is needed to meet public access needs and/or to
supplement the fleet’s time fill capability.
Advance Fuel Systems, Corp.
9102 E. 46th. Street
ulsa, OK. 74145