The answer to 'when to service system upgrade' is that you should service your HVAC system every 1-2 years, or as recommended by the manufacturer. Regular maintenance helps ensure your system is running efficiently and identifies any issues before they become major problems. This includes cleaning or replacing air filters, checking refrigerant levels, inspecting electrical components, and testing the thermostat.
If your system is over 10-15 years old, or you notice significant performance issues like inconsistent temperatures, high energy bills, or frequent breakdowns, it may be time to consider upgrading to a newer, more energy-efficient model. A professional HVAC technician can evaluate your current system and provide recommendations on the best time to upgrade.