LNG and CNG are not different fuels — they are the same fuel, predominantly methane, stored two different ways. CNG (compressed natural gas) keeps the methane as a gas squeezed to high pressure at ordinary temperature. LNG (liquefied natural gas) instead chills it to a cryogenic liquid. That single choice — compress or liquefy — sets everything that follows: how much energy fits in a tank, how far a vehicle can travel, how heavy and costly the tank is, and what kind of refuelling infrastructure is needed. The result is a clean division of labour: CNG dominates short urban journeys near a pipeline, while LNG dominates long-haul and off-grid transport.
The same molecule, two storage methods
Natural gas is mostly methane, and at room temperature and pressure it is extremely diffuse — a fuel tank full of it at atmospheric conditions would hold almost no usable energy. To make it practical to carry on a vehicle, the gas must be packed into a much smaller volume. There are only two ways to do that:
- Compress it. CNG is squeezed to roughly 200-250 bar while staying at ambient temperature. That high pressure forces the molecules together, achieving about a 200:1 volume reduction. No refrigeration is involved.
- Liquefy it. LNG is cooled to about -162°C, at which point methane condenses into a liquid at near-atmospheric pressure. Liquefaction packs the molecules far more tightly than pressure alone, giving roughly a 600:1 volume reduction.
Both end products burn the same way in an engine and produce the same combustion chemistry. The distinction is purely about storage: pressure versus cold. For the underlying science of why liquefaction achieves such a dramatic reduction, see the physics of LNG.
Energy density: the heart of the difference
Because liquefaction packs the gas more densely than compression, LNG stores substantially more energy in the same space. CNG at typical storage pressure holds roughly 9 MJ per litre; LNG holds around 22 MJ per litre. In practical terms, a litre of LNG carries roughly two to two-and-a-half times the energy of a litre of CNG.
This is the single most important number in the comparison. A vehicle has only so much room for fuel tanks, so higher energy density translates directly into longer range — or, for the same range, smaller and lighter tanks. CNG's lower density means its tanks must be larger and heavier to carry a useful amount of energy, which eats into payload and limits how far the vehicle can go between fills.
LNG and CNG side by side
The table below summarises how the two storage methods compare across the properties that matter for choosing one.
| Property | CNG | LNG |
|---|---|---|
| State | Compressed gas | Cryogenic liquid |
| Storage pressure | ~200-250 bar (high) | Near-atmospheric (low) |
| Storage temperature | Ambient | ~ -162°C |
| Volume reduction | ~200:1 | ~600:1 |
| Energy density | ~9 MJ/L | ~22 MJ/L |
| Typical vehicles | Cars, city buses, light commercial, short-range fleets | Heavy long-haul trucks, ships, rail |
| Range | Shorter (bulky, heavy tanks) | Longer (dense fuel) |
| Infrastructure | Compressor at any pipeline connection | Insulated cryogenic tanks; boil-off management |
These figures are approximate and vary with tank design, gas composition, and how full the tank is allowed to run. The relationships between them, however, are consistent and explain most real-world fuelling choices.
Tanks, weight, and cost
The two storage methods impose very different demands on the vehicle. A CNG tank is a pressure vessel: it must withstand 200-250 bar, so it is built thick and strong, which makes it heavy and bulky relative to the energy it holds. But it needs no insulation or refrigeration, so it is mechanically simpler and cheaper to manufacture, and the fuel inside does not gradually evaporate.
An LNG tank is the opposite kind of vessel: it operates at low pressure but must keep its contents near -162°C, so it is essentially a high-performance vacuum-insulated flask. That makes it more expensive and adds a second issue — boil-off. Heat slowly leaks in, evaporating a little of the liquid, so the tank must vent or otherwise manage that pressure. A vehicle that sits unused for long periods can lose fuel this way, which is why LNG suits vehicles in near-constant use. CNG has no boil-off and can sit indefinitely.
Which one fits which job
The properties above sort the two fuels into fairly clear roles.
CNG: short range, near the pipeline
CNG suits passenger cars, city buses, refuse trucks, light commercial vehicles, and other short-range fleets that return to a depot. Its decisive advantage is infrastructure: anywhere the pipeline grid reaches, a compressor station can fill tanks directly from the line, with no cryogenics and no cold-chain logistics. The cheaper tanks and absence of boil-off make CNG well matched to predictable urban duty cycles where the daily range is modest.
LNG: long range, heavy loads, off-grid
LNG suits heavy long-haul trucks, ships, and rail — applications where high energy density and long range matter, and where the weight of CNG tanks would be prohibitive. It is also the answer wherever there is no pipeline: LNG can be trucked to remote sites and stored as a virtual pipeline supply, delivering gas to places a fixed line will never reach. The price of that reach is cryogenic tanks and boil-off management.
Where the two meet: LCNG stations
The line between the two is not absolute. Some refuelling sites receive LNG by truck and then warm and pressurise part of it on the spot to dispense as CNG — an arrangement known as LCNG. This lets a location offer compressed gas without any pipeline connection at all, using LNG as the delivery vehicle and CNG as the dispensed product. A single LCNG station can serve both LNG-fuelled long-haul trucks and CNG-fuelled local vehicles from one cryogenic supply, which is useful in regions where the grid is sparse but demand for gas vehicles exists.
So which is "better"?
Neither, in the abstract — they answer different needs:
- Choose CNG when pipeline gas is available, journeys are short, tanks can be refilled at base, and lower tank cost matters more than range.
- Choose LNG when range and energy density are decisive, loads are heavy, or no pipeline exists and the fuel must be delivered as a liquid.
In short, CNG is the simpler choice wherever pipeline gas is on hand, while LNG wins on range and density for the heavy and the remote. Many networks use both, and LCNG stations let a single site bridge the two.
Frequently asked questions
Are LNG and CNG the same fuel?
Yes. Both are predominantly methane — the same product stored two different ways. CNG is natural gas compressed to roughly 200-250 bar at ambient temperature. LNG is the same gas cooled to about -162°C until it becomes a cryogenic liquid at near-atmospheric pressure. Once delivered to an engine and burned, they behave identically.
Why does LNG store more energy than CNG?
Liquefying gas packs the methane far more densely than compression can. LNG achieves roughly a 600:1 volume reduction and about 22 MJ per litre, while CNG at 200-250 bar achieves about 200:1 and roughly 9 MJ per litre. So a litre of LNG holds roughly 2 to 2.5 times the energy of a litre of CNG, which translates into longer range from the same tank size.
When should a fleet choose CNG over LNG?
CNG suits passenger cars, city buses, light commercial vehicles, and short-range fleets that return to base and can refuel directly from the pipeline grid. Its tanks are cheaper because they need no cryogenics, and a compressor station can be installed wherever pipeline gas is available. The trade-off is bulky, heavy tanks and shorter range, which is acceptable for predictable urban routes.
What is LCNG?
LCNG describes a station that receives LNG by truck, stores it as a cryogenic liquid, and then warms and pressurises some of it on site to dispense as CNG. This lets a location offer CNG without a pipeline connection, using LNG as a virtual pipeline to deliver the gas. Such stations can serve both LNG and CNG vehicles from the same supply.