As a responsible homeowner, you try to keep up with basic HVAC maintenance, and that means checking your HVAC filter on a regular basis, and changing it when it looks clogged or dirty. However, for folks living in areas with defined season changes (which includes Southern California), the frequency of air filter changes will depend on the seasons and what sort of system you operate.
If your home uses a furnace for heating and an A/C for cooling, the air conditioner’s evaporator coil is likely attached to the furnace, and uses the furnace blower to blow air across the coil and then distribute it throughout the house, via ducts and registers. The air filter typically is located in the furnace, near where the ductwork is attached. In this case, you’ll want to check the furnace’s air filter at least once a month during any season when cooling or heating is being used.
If your home uses a heat pump for both cooling and heating, the air filter will be located in the system’s air handler. As with the preceding situation, you should check the filter monthly, and change it when necessary, during both heating and cooling seasons. During the in-between seasons, fall and spring, when not much heating or cooling is needed, it’s still a good idea to expend a minute or two once a month to check the filter. However, you won’t need to change it nearly as often.
In all cases, a clean HVAC air filter will maintain smooth air circulation, whereas a clogged filter will force the system to work harder to push air through. This wastes energy, stresses parts, and leads to longer heating and cooling cycles. Your home will take longer to get comfortable. A dirty filter also allows dirt and debris to get into sensitive system components, which impairs efficiency and performance.