CNG is generally stored at 3000 or 3600 psi when used in a vehicle. Lower pressure means less fuel and shorter range. Natural gas pipeline pressure is only 500 psi and a process must occur to pressurize the natural gas to this higher psi. There are two general methods of compressing and filling natural gas for tranportation:

1. Private/Home - Slow Fill
   • Natural gas flows from your home's or business' natural gas line and is pressurized into your vehicle's tank. Slow fill refueling times vary widely depending on tank volume and compressor type. Most compressors range between .5 GGE / hour and 5 GGE / hour. The user pays for the natural gas and electricity.
2. Public - Fast Fill
   • At fast-fill CNG stations, gas is compressed prior to your arrival and transferred to a large storage tank. When you arrive at the station you transfer a portion of the compressed gas in the storage tank into your vehicle. This process takes a few minutes and is comparable to filling your vehicle with gasoline.

New technologies are under development that could lower tank pressure, provide tank flexibility in size and shape, and increase vehicle range.