Refrigerant charge refers to the specific amount of refrigerant in an HVAC system. Proper charge is critical — both overcharged and undercharged systems operate inefficiently, experience increased wear, and may fail prematurely.
An undercharged system (too little refrigerant) runs longer to achieve setpoint, may not cool adequately in hot weather, can cause the evaporator coil to freeze, and stresses the compressor. An overcharged system has excessive head pressure, reduced efficiency, and can damage the compressor with liquid slugging.
Refrigerant charge must be verified by a certified HVAC technician using a manifold gauge set. Charging methods include weighing refrigerant in by weight, superheat measurement (for fixed orifice systems), and subcooling measurement (for TXV systems). A properly charged system typically needs no refrigerant additions over its lifetime — refrigerant is not consumed, only lost through leaks.