The answer to 'when to service HVAC system' is that you should service your HVAC system at least once a year, typically in the spring before the cooling season and in the fall before the heating season. Regular maintenance helps ensure your system is running efficiently and can prevent costly breakdowns.
During a maintenance visit, an HVAC technician will inspect the system, clean the components, and perform any necessary adjustments or minor repairs. They may also recommend replacing air filters, which should typically be done every 1-3 months depending on usage and indoor air quality.