Central Air Conditioning Buyer’s Guide

The outdoor or hot side of a central air conditioning system consists of the compressor and condenser coil.

In most cases it will be most cost effective to install a central air conditioner when your home is being built. Even if an existing home doesn’t have central A/C, as long as it already has ductwork and a central heating system, retrofitting air conditioning can be relatively straightforward and cost effective. Older homes that do not have a central heating system will involve greater cost and complexity since ductwork must be added.

Regardless which of these three scenarios you are facing, this guide will help you understand central air conditioning concepts, components, equipment brands, contractor selection and costs and is intended as a helpful resource for both homeowners and contractors alike.

While most do-it-yourself homeowners and general contractors will opt to have a central air conditioning system installed professionally, its important to understand how central air works, the components required, which manufacturers and brands to consider and how to get the highest quality installation services at the best value.

Whether you are building a new home or doing major renovation on an older home, a central Heating and Air Conditioning (HVAC) system is a major component and provides a very good return on investment for the homeowner, improving the overall comfort and resale value of the home. There are three main things to consider when shopping for a home A/C system; cooling capacity, efficiency and service life.

How Central Air Conditioning Systems Function

The fundamental concept behind any air conditioning system relies upon the law of thermal dynamics which states that if hot and cold spaces are separated by a “medium” the transfer through the medium is from hot to cold.

Heat follows cold, so a central air conditioner draws warm, humid air across fin tubes on the evaporator coil. This causes the air to condense. Moisture is collected in a pan below the coil and drained off, helping reduce humidity inside the living space.

The coil must be continually cooled, which is the function of the compressor and condenser coil in the outdoor unit; hot air is returned from the air handler to the compressor. The compressor pressurizes liquid/gas refrigerant, heating it to a gaseous state and sending it to the adjacent condenser coil, where it is cooled and returned to the evaporator unit indoors.

This repeated cycle of removing warm air from inside the house to outside and pumping in cooler air is, of course, what makes the temperature inside the living space more comfortable on a hot day! The amount of energy needed to cool your home is an important factor in determining the overall cost of operating your central air conditioner.

Central air conditioning systems work by repeatedly pumping cool air into your home and removing hot air.

Central Home Air Conditioning Components

HVAC system components are generally divided between indoor and outdoor appliances, with the heat-producing, heaviest components such as the compressor and condenser coil located outside the home and the evaporator being installed in the plenum of the furnace, typically in the attic space, garage or other service location indoors. These indoor and outdoor segments are connected a low-voltage relay cable and refrigeration lines.

In most cases, the cool air will be circulated into the home via insulated, flexible ductwork installed in the attic space and/or under the subflooring to vents in the ceilings, walls and/or floors inside the living space. This is very cost effective in a home that uses forced-air heating as well. If the home uses a radiant floor heating or baseboard heating system, the overall cost of installing ductwork for central air conditioning entails additional expense since a dedicated blower and ductwork are required for the central air conditioner only in this case.

Carrier Corporation and other manufacturers also offer a ductless system, which employs several smaller indoor evaporator coils, each with a blower to circulate air within a given portion of the living space. The units are installed in exterior walls, with refrigeration, condensation and electrical lines running outside the house from each evaporator back to the outdoor compressor unit.

The costs of a ductless versus traditional system must be weighed to determine which is more cost effective and will be based on the size of the home, cooling capacity required, number of evaporators required and distance from each to the compressor unit. A ductless system is typically only used in a home without forced-air heating; otherwise cost and simplicity make ductwork the better route in the majority of cases.

Central Air Conditioning Cost Factors

Of course the up front cost of a central a/c system includes the air conditioning components, the ductwork, contractor labor and building permits, which can run from as little as about $3,000 to over $7,000. To replace an existing system could cost less than $2,000 if the ductwork, wiring and other non-system components are operable and do not require replacement.

Perhaps more important is determining the ongoing cost of operating and maintaining the system. As a result of the National Energy Conservation Policy, new regulations were introduced in the United States in 1990 to establish minimum energy efficiency standards for heating and cooling equipment. This has helped enhance efficiency dramatically from the systems made fifteen or twenty years ago!

The rating given to new central air conditioner condenser units is known as the Seasonal Energy Efficiency Rating (SEER), which is determined by dividing the cooling capacity of an air conditioner by the electrical input needed to operate the unit. The lowest SEER now allowed for new units is now 13. The highest-rated systems currently available are SEER 20. These ratings have improved dramatically in the last ten years and will continue to improve even further.

Higher efficiency is achieved primarily by using more efficient, multi-speed compressors and increasing the size of the condenser coil and fin tubes. Additionally, new units use R4-10A refrigerant instead of the ozone-depleting CFC R22 refrigerant (Freon) used previously, making them more environmentally friendly.

Central Air Conditioning System Capacity and Efficiency

A licensed, experienced HVAC contractor should be able to size and specify the equipment best suited to your home, factoring the age, quality of windows, insulation, number of floors, square and cubic feet of living space, and local factors such as climate, humidity, local energy costs and average number of days the system will be needed to operate annually.
If your system is too small it will work too hard and if it’s too large, it may cycle on and off too frequently, reducing efficiency and the ability to reduce humidity inside the home.

It takes years of experience to know how to properly size and specify a central air conditioning system so leave it to a pro. Consult several reputable HVAC contractors to compare their specifications, opinions and recommendations before you make a final decision.

Deciding how much efficiency you need is a matter of personal economics, comfort level and environmental concerns. You may or may not save enough on a SEER 15 or higher system to offset the higher installation costs versus the lower ongoing costs of operating a system with a lower SEER.

With rising energy costs, the economics are shifting, so that the additional $200 or $300 it costs to increase your system from one SEER to the next might easily pay off over the service life of the system, especially if you live in a very hot climate where air conditioning is needed frequently!

The other important factor to consider is the warranty terms; paying more up front could save you money down the road. Proper installation may be more important to getting the maximum service life than the system components, so be sure your HVAC contractor is trained and certified by the manufacturer whose equipment is being installed. Also consider purchasing an extended warranty or maintenance contract on your central air conditioning system.

Central Air Conditioning Equipment Brands

While many other suppliers exist, we have provided basic dealers on the most prominent north American HVAC manufacturers below:

Carrier and Bryant

Both owned today by United Technologies Corporation, Carrier and Bryant are probably the most widely recognized brands in north America and the largest manufacturer worldwide. Willis Haviland Carrier is credited with inventing the modern air conditioner in 1902, launching Carrier as a premier manufacturer in the industry.

Charles Bryant followed Carrier, founding Bryant in 1904. Between these two brands, UTC offers hundreds of products including air conditioning systems, heat pumps, furnaces, boilers, duct free systems, ventilators, controls, thermostats, humidifiers, air purifiers and more.

Carrier and Bryant home comfort systems include multiple product lines within both brands to meet almost any home central air conditioning system needs.


In business since 1982, Goodman Manufacturing is known as a low cost provider of central air conditioning systems. Founded by ex-air conditioning contractor, Harold Goodman, the company focuses on providing affordable, reliable cooling and heating products, backed by industry-leading product warranties.


Founded in 1895 in Iowa by Dave Lennox, who invented the world’s first riveted-steel furnace, Lennox Industries continues to make some of the most efficient air conditioning systems on the market, with over 60 leading-edge products and a network of over 6,000 dealers.

Today, Lennox’s claim to fame is having introduced the first SEER 20 air conditioning system, pushing the efficiency envelope to new limits!


Norwegian immigrant James Trane founded his company in Wisconsin in 1885 with the invention of the innovative, low-pressure Trane Vapor Heating System. Nearly 100 years later, Trane acquired the air conditioning unit of General Electric to become a leading supplier in the industry.

Innovation continues to drive Trane, which now operates as a unit of Ingersoll Rand, offering systems under the Trane and American Standard brands. Promoting the trend to combine air purity and comfort, Trane offers whole-house systems designed to remove almost 90 percent of the particles and allergens from air inside a home’s living space!

York, Luxaire and Coleman

Johnson Controls Company owns these industry brands, offering a complete line up of home air conditioning products and a large network of distributors and dealers. A storied history led to these three brands coming under the ownership of Johnson Controls, which offer a complete product lineup that competes against the other two major north American manufacturers; Trane and UTC.

Central Air Conditioning Buying Tips

  • When buying a new HVAC system, the most important decisions to make are selecting the right local company to install and service the system and the efficiency rating and home air comfort features you need; you can go basic or spend a lot more adding whole-house filtration and humidifier, programmable controls and lots of other bells and whistles!
  • The brand names are confusing and somewhat misleading, since the big three manufacturers (UTC, Trane and Johnson) control a large portion of the market today. Seek advice from others and look at features, ratings and warranty terms to make the right selection. Shop around and get multiple quotes once you know which brand and equipment specifications you want; with labor, equipment and other factors you can find a wide variance in the prices quoted by local HVAC companies!
  • Correct sizing is critical; again you want a system that is neither too large nor too small for you home. If you have a home with more than 2 levels, you may need multiple, smaller air handlers to increase efficiency versus going with one larger unit.
  • The three primary considerations in calculating system load are local climate, area to cool and the envelope of your home, which is the interface between the home and the outside world. Within these three categories there are many factors that affect the “load” and “optimal” size and specifications of your air conditioning system.
  • Pay attention to the efficiency ratings when purchasing air conditioning system components; know the SEER and AFUE (Annual Fuel Utilization Efficiency) in order to estimate and compare your ongoing operating costs.
  • Make a list of “must have” and “nice to have” features when pricing systems; this way you can ask each prospective contractor to provide low and high estimates before deciding how much cash you want to invest!
  • Ask about special financing, incentives and rebates and let your contractor know you are shopping around; if you don’t insist on the best price and value you won’t get it. As in many businesses, the supplier who most values your business will demonstrate it through the service, price and satisfaction delivered!
  • When upgrading or replacing an existing central air conditioner (especially if the furnace does not need to be replaced), ask several contractors to evaluate which components need to be replaced and which of the existing components could be reused to cut down the total cost; matching system components correctly is very important in this case. Rebates may also be available so be sure to ask.
  • Consider purchasing an annual maintenance agreement; you want to have the A/C side of the system inspected in the spring and the heating side checked in the fall.
  • Be sure to schedule maintenance during these off peak times of the year to avoid problems when you need your system the most; you don’t want to try and schedule home air conditioning system installation or maintenance during the middle of a heat wave!

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