Delta T refers to the difference in temperature between the air entering your unit and the air coming out of it. For a system that is cooling properly, you typically want to see a temperature drop of about 15 to 20 degrees Fahrenheit. This simple test is the fastest way for a homeowner to check if their Wall Mount unit is performing as it should. If the Delta T is too low, it could mean the filters are dirty or the system is low on refrigerant. We offer Replacement Air Filters to help you maintain that ideal temperature drop. You can measure this using a basic digital thermometer at the intake and the vents of your air handler. Our Technical Data section explains more about expected performance levels for different series. Monitoring Delta T is a core part of Preventive Maintenance and overall system health checks.