Abstract: A one or two piece insulated jacket with electric heating elements is provided for placing around a portable cylinder of refrigerant for charging air conditioners and refrigerating units and heat pumps. A thermostat may be provided for regulating the current from a power source to the heating elements to control the temperature inside the insulated jacket. The insulated jacket may be extended across the bottom of the cylinder and a heating element placed there. The bottom of the jacket may have a pocket for a weighing scale to determine how much fluid has been used to charge an air conditioner. A method of transferring refrigerant utilizing a thermostatically controlled heating jacket around a refrigerant portable container is provided.