During the hot summer months in Texas, HVAC system is a leading energy consumption device in every homes across the state. From my past experiences, (I have worked in the HVAC field for the past 5 years while going to school), I heard people complaining about the high electric bills of their AC system. They would called an AC service company and see if they need the freon recharge or a tune up on their AC system. That could somtimes cost a fortune. As a matter of a fact, in most cases, only simple steps are needed to fix the problem -- as simple as, for example, to change a filter or to clean the coil.
From June to September, 3 out of 4 service calls that complained about the high electrical bill were not related to freon level or the inner components of the AC system. Instead, they are related to the filth of the condenser or the evaporator coil. Dirty coil causes the efficiency of the AC system to go down. It is due to the dirt, hair, grass or leaves clogging the coil, that less heat is exchanged from the air to the system or system to air. This creates a longer compressor running time and as a result, the high electricity bill. (Compressor is a piece of component that uses majority of the electricity in the AC system.) Below is a picture of the dirty indoor coil with dirty filter. (www.homespecny.com/
In order to keep the AC efficiency high at your home, a routine maintenance is necessary. I will discuss a few of the routine maintenance procedures that a home owner can do at home. This will eliminate the need to call a AC service company and keep the bills low.
(1) Change filter regularly. This will prevent the indoor coil from getting dirty. In the summer months, it is best to change filter once a month. Due to the the high fan speed operation at the cooling mode , the amount of air passes through the filter is increased. As a result, filter gets dirty easier. The filter you should purchased is preferable to be the pleated filter, not the blue mesh filter (the latter one is cheaper, but definitely not the right kind). Blue mesh filter is a pre-filter for the pleated filter so that the pleated filter can last 2-3 months theoretically. During the winter months, it is OK to change to filter once every 1.5-2 months. This is because the fan speed is set at low speed for most of the system in the heating mode. This will create less air exchange, therefore prolong the filter life.
(2) Clean the condenser- the outdoor unit. Here is a picture of what a dirty condenser looks like. (www.martynmechanical.com/)
The best way for the home owner to clean their condenser without removing the electric panel, outside panels and fan assembly is to go to Home Depot and buy the self rinse condenser coil cleaner. This cleaner will only work for removing limited amount of debris. If the condenser is as dirty as the one shown in the picture, it is better to get a professional cleaning. After cleaning, you should keep it up every year with a couple cans of self rinse coil cleaner. A proper way for a AC professional to clean your condenser unit is, first of all, remove all the panels and fan assembly, secondly, apply coil cleaning chemical on the coil, and the final step, is to spread the coil from inside out with water. The last step is very important because by spraying the water from inside of the coil to outside, we can prevent pushing the debris further into the coil.
The chart above shows the operating cost of clean coil VS dirty coil. (www.gbenvironmental.com/