Inside your warm house, cold liquid refrigerant evaporates on the evaporator coil, turning into gas. The hot refrigerant gas is then pumped outside into your system's condenser, where it transfers the heat to the outside air and reverts into a liquid again and the cycle continues [source: DOE].
As you can imagine, if the refrigerant is low, the air conditioner won't cool very well. The amount of the refrigerant in the unit must exactly match the manufacturer's specifications
There are two reasons why you would have a low level of refrigerant. One is that when the system was installed, not enough was added. But more likely, the level is low because your system has developed a leak.
Leaks are the cause of 90 percent of the cases of low refrigerant [source: ServiceExperts]. So, simply adding more refrigerant isn't going to fix things. Bring in a trained technician to find the leak and fix it. After the repair is tested, the technician can charge the system with the correct amount of refrigerant and your system should be set.
Nearly all current AC systems use halogenated chlorofluorocarbons (HCFCs), aka R-22 or freon, as a refrigerant but these are being phased out for environmental reasons. Between 2020 and 2030, ozone-safe hydrofluorocarbons (HFCs) are expected to become the norm [source: DOE].