Abstract: A method and apparatus for introducing a compressed gas into a pressure vessel, for instance, hydrogen into a vehicle fuel tank, in which hydrogen is compressed in an initial and final compressions stages which can be powered by a common source. The initial compression stage can continually operate to compress the gas in a lower pressure storage bank during the time that hydrogen is dispensed to a vehicle fuel tank. In time periods between dispensing, the gas from the lower pressure stage and from the lower pressure storage bank is compressed in the final compression stage and stored in a higher pressure storage bank. When the pressure vessel is to be filled, the compressor compresses the gas from the higher pressure storage bank to fill the vessel.