The question “How often should a central AC unit be charged with refrigerant?” is more important now than it has ever been. New rules about refrigerants, old HVAC systems, and the need for more cooling are making homeowners and building managers rethink how to look after their AC.

Even though new environmental rules are pushing people to go with cleaner and more efficient refrigerants, older systems are still common in places like New York. At the same time, central air conditioning systems are taking on more work because summers are getting hotter and cooling seasons are stretching out. The old idea of “just adding more refrigerant” doesn’t cut it anymore because of the ongoing switch to newer refrigerants.