Energy Efficiency of Your Air Conditioning Units

Global warming effects us all and in countries where air conditioning units which were once considered an extra expense item, seem to be the only offering of relief from the hot sultry weather outside. The inevitable question which arises is how much power are these air conditioning units utilizing? Let’s take a look.

The results from a survey by energy information administration will help us understand the facts better. In 2001 a survey was conducted which calculated the total amount of carbon dioxide that was being released into the air by homes in the United States. It was found out that 15% of the total amount of energy consumption was accounted for by air-conditioner use (Around 182 billion kWh of electricity per year), which significantly increased the total amount of carbon dioxide in the air. The amount of carbon dioxide produced to generate that amount of electricity is estimated at 119 million tons. (Equivalent to CO2 expelled by 20 million cars per year in US).

Central air-conditioning system or the window units?
If you want to air-condition your home or office you  have many different choices the usual suspects are the window or central air units. The precariously dangling window air conditioning systems consist of an integrator, a condenser, an army of fans and a thermostat to regulate the temperature. In the case of central air-conditioning systems, the architecture is completely different. In this case a condenser is installed at the backyard or on the roof and several cooling pipes that carry the coolant run through the entire house and end up at the vent which is often located near a fireplace. The air handler near the fireplace is responsible for blowing cold air into individual rooms with the help of the home’s cooling duct system.

There are basically two things that are totally related to the vast amount of energy consumed by air-conditioning units – environmental concern and hefty bills at the end of the month. Though there is no clear evidence to prove that central air-conditioning systems are actually better than the window units in terms of the environment and total power consumption but there are few important technical aspects to consider.

Air conditioners are not only tasked with regulating the temperature in the room but also the total amount of humidity. If an air-conditioning unit removes very small amount of moisture and quickly cools a small amount of air to subzero temperatures, it has to work at its full speed which is the case with window units in individual rooms. While as the central air-conditioning systems with their variable speed settings are better equipped to handle the humidity by processing larger volumes of air, they cool each unit volume by a lesser amount than window unit. This is where the central cooling surpasses the window units in terms of energy consumption.

The efficiency rating also varies between central cooling and window units. In the case of central cooling the efficiency of the air-conditioning unit is measured in 2 ways. The most common way is ‘energy efficiency ratio’ (EER) which basically refers to the total amount of energy that is used by the air-conditioning unit for cooling 95° air (a prescribed volume) under laboratory conditions in one hour. The other method is ‘seasonal energy efficiency ratio’ (SEER) which refers to average energy used at different temperatures and humidity levels. The energy rating for window units are measured only by using EER and not by SEER because it can’t work at a range of speeds like central units. The window units need to be in the range of 9.4 and 10.7 EER in order to be certified, where as a certified central air-conditioning system at least have an energy efficiency ratio of 12.

Window units also have got their positive points over central air units. Central air-conditioning systems are better equipped to handle the humidity, but since they have a lot of ducts, these get clogged with cool air which then warms up and tend to leak through the fittings. This can result in decrease of energy efficiency up to 30% and the problem overshadows the solution.

Other advantage of window units is that it begs for attention like a child by shaking violently whenever the condenser switches on. It won’t let you go out without switching it off! On the other hand, quiet and unnoticeable functioning of central-unit, causes an accidental overuse by forgetful users. Individual room units can further save energy by their room-to-room usage. When it’s supposed to cool only a single room it can consume a very small part of energy which the central unit would have used otherwise.

The evolution of central units has made them smarter with programmable thermostats that allow you to set a power-down time and they also allowing you to divide your house in separately controlled zones. Some central air-conditioning systems are also available that do not have any ducts in them and these can generally outperform the old-school central air-conditioning systems and the window units – but, they are costly!
Let’s get back to the question that we started off with at the beginning of the article. Each kind of air-conditioning unit has its own set of advantages and disadvantages and the total energy consumption depends completely on the kind of hardware that is being employed. So, when choosing an air conditioner for your home, you need to take a look at the technical specifications before making your decision. If you have a large room and there isn’t a lot of humidity in your area, the window units would probably suffice. But, if price doesn’t matter to you, the central air-conditioning systems (the ductless variety) should be opted for.

Author Bio:
My name is Carles Kimber from advancedaircontrol.net. I research and write about the topics related to energy consumption by appliances in United States.

Photo Credit:  Some rights reserved by Ran Yaniv Hartstein

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