Abstract: A heat pump for use in heating residential, commercial or industrial buildings, industrial and agricultural processes and heating of water to moderate temperatures such as may be required in swimming pools or as a water pre-heater for any other use. The system includes a fuel consuming refrigerant boiler for producing a refrigerant in vaporized form at relatively high pressure, the output of the boiler being connected to a superheater and then to the primary jet of an ejector-type compressor. An evaporator unit exposed to ambient temperatures has its output line connected to an inlet of the ejector such that as the high pressure gaseous refrigerant flows through the nozzle of the ejector, a low pressure is created and the refrigerant from the evaporator is also caused to flow through the ejector compressor to a condenser where the refrigerant is allowed to give up its heat.