A vapor compression system comprising: a variable speed single stage compressor to compress a refrigerant to a high pressure, the compressor including a suction port, a discharge port, and an economizer port; an economizing heat exchanger; a heat accepting heat exchanger for exchanging heat between the refrigerant and an airflow to heat the refrigerant and cool the airflow, wherein the airflow is provided to an area; a temperature sensor to detect an air temperature of air in the area; and a controller that adjusts a speed of the variable speed single stage compressor based on the air temperature to match a cooling load requirement of the vapor compression system to cool the area; characterised in that the variable speed single stage compressor includes a compression chamber, a piston that moves in the compression chamber, and a seal disposed between the piston and the walls of the compression chamber, wherein during a suction stroke the piston moves in a first direction to expand a volume of the compression chamber and blocks the economizer port to prevent the refrigerant in an economized path from entering the compression chamber and during a discharge stroke the piston moves in an opposing second direction to reduce the volume of the compression chamber to compress the refrigerant and blocks the economizer port to prevent the refrigerant in the economized path from entering the compression chamber, wherein during the suction stroke of the piston a pressure-operated suction valve opens to allow refrigerant from a heat accepting heat exchanger into the compression chamber and a pressure-operated discharge valve is closed, wherein during the discharge stroke of the piston the pressure-operated discharge valve opens to allow the refrigerant to exit the compression chamber and flow toward a heat rejecting heat exchanger and the pressure-operated suction valve is closed, and wherein toward the end of the suction stroke the piston no longer blocks the economizer port such that refrigerant at intermediate pressure enters the compression chamber from the economizer port and closes the pressure-operated suction valve, preventing refrigerant from entering through the suction port. a variable speed single stage compressor to compress a refrigerant to a high pressure, the compressor including a suction port, a discharge port, and an economizer port; an economizing heat exchanger; a heat accepting heat exchanger for exchanging heat between the refrigerant and an airflow to heat the refrigerant and cool the airflow, wherein the airflow is provided to an area; a temperature sensor to detect an air temperature of air in the area; and a controller that adjusts a speed of the variable speed single stage compressor based on the air temperature to match a cooling load requirement of the vapor compression system to cool the area; characterised in that the variable speed single stage compressor includes a compression chamber, a piston that moves in the compression chamber, and a seal disposed between the piston and the walls of the compression chamber, wherein during a suction stroke the piston moves in a first direction to expand a volume of the compression chamber and blocks the economizer port to prevent the refrigerant in an economized path from entering the compression chamber and during a discharge stroke the piston moves in an opposing second direction to reduce the volume of the compression chamber to compress the refrigerant and blocks the economizer port to prevent the refrigerant in the economized path from entering the compression chamber, wherein during the suction stroke of the piston a pressure-operated suction valve opens to allow refrigerant from a heat accepting heat exchanger into the compression chamber and a pressure-operated discharge valve is closed, wherein during the discharge stroke of the piston the pressure-operated discharge valve opens to allow the refrigerant to exit the compression chamber and flow toward a heat rejecting heat exchanger and the pressure-operated suction valve is closed, and wherein toward the end of the suction stroke the piston no longer blocks the economizer port such that refrigerant at intermediate pressure enters the compression chamber from the economizer port and closes the pressure-operated suction valve, preventing refrigerant from entering through the suction port.