Abstract: A refrigerant storage reservoir, connected by valves to the high and low pressure lines of a refrigeration system, and controlled by a microprocessor based system that monitors temperatures and pressures, provides a means of regulating the overall amount of refrigerant charge in a heating or cooling system to optimize economy or performance during operation. Reference temperature and pressure data profiles, permanently stored in memory, are compared with actual data collected while the refrigeration system is operating. If a reduction of refrigerant charge is indicated, a valve on the high pressure side of the refrigeration system is opened to allow excess refrigerant to flow into the storage reservoir. If an increase in refrigerant charge is indicated, a valve on the low pressure side of the refrigeration system is opened to allow refrigerant to flow from the reservoir into the operating loop of the refrigeration system.