When you install a brand new heating, ventilation and air conditioning (HVAC) system, you will be told the amount of energy the system consumes to cool or heat a given area. After some time, however, the HVAC may start consuming more energy than it should be consuming. Here are some of the things that can contribute to such a drop in HVAC efficiency:
The Filters Are Dirty
The filters trap contaminants from the air so that you don't have to breathe in dirty air. This means the filters get dirty over time, and they need to be replaced. Most filters need to be replaced at least once every two months. However, you may need to change them more frequently than that if you have pets in the house or live in a dusty neighborhood; such things make filters dirty rather quickly.
If you haven't been replacing the filters as required, then they are probably dirty and hindering airflow. In that case, the system has to use more energy to force air through the dirty filters, which is probably why you are experiencing reduced efficiency.
Your Load Capacity Has Increased
HVAC systems are designed to serve specific square footage; that's why your technician needs to know the size of your house before installing one. However, your HVAC system's load may increase even if the size of your house hasn't increased. For example, if your insulation is damaged, conditioned air will be escaping your rooms meaning your HVAC will need to work extra hard to condition the fresh air from outside. Another example of increased load is the installation of heat-producing lights, such as the old-fashioned fluorescent lights. If you didn't have such lights when installing your HVAC, the increased heat they will be producing would require more energy to remove, leading to decreased energy efficiency of the system.
You Have Not Been Maintaining the System
Lastly, your system may be experiencing reduced energy efficiency due to poor service. The HVAC has many parts that need to be serviced to continue operating efficiently. For example, both the evaporator and condenser coils, which aid in heat exchange, need to be kept clean. A buildup of dirt over the coils will interfere with heat transfer and affect energy efficiency. Apart from that, you also need to check for refrigerant leaks, which reduce the volume of refrigerant flowing through the coils and interfere with the heating/cooling efficiency of the system.
As you can see, many things that can interfere with your HVAC system's energy efficiency. Therefore, you may not be able to identify the cause of the problem without a thorough examination of the system. A professional HVAC contractor can help you with the diagnosis and fix.