Your HVAC should be serviced twice a year, once during the fall and once during the spring. This is done to ensure that the machinery is clean, that its parts are in good condition, and that it is operating as efficiently as possible. HVAC contractors focus on your furnace in the fall to ensure it is ready for the cold. Then air conditioner tune-ups are scheduled in the spring after the weather has warmed up, so you can be ready for the summer heat and humidity.