All of us like to be comfortable indoors, even when it is hot and humid outdoors.  We also like to keep our utility bills under control.  What is the most efficient way to run your central air conditioner?  This HVAC guide will give you tips for staying cool without blowing the budget on high energy bills.

Tip #1: Set your Thermostat to 78

That might sound too warm, but for most people, 78 will be comfortable, especially with the lower humidity levels that are produced by air conditioning.  A home that is 78 degrees with the 35% to 40% humidity that ACs can feel as cool as 72 or 74 with higher humidity.

Tip #2: Use a Programmable Thermostat and Turn Up the Heat When Away

Is your home empty during the day or for long stretches?  Turn up the temperature to 85 while you’re away.  Program the system to come back on and lower the temperature before you are scheduled to get home.  You won’t know the difference!  Your pets probably won’t either, especially if you leave them plenty of cool, fresh water.

Tip #3: Vent your Attic

That may sound like an odd one, but it is vitally important.  In the summer, heat builds up in a poorly ventilated attic and pushes down into the house, making it warmer and causing the air conditioner to work extra hard to keep the house cool.  Several properly located vents in the attic will pay for themselves quickly as you reduce your air conditioning usage. It will help your roof last longer too, and reduce the chance of mold taking root in your home.

Tip #4: Use a Fan to Circulate Air

Moving air feels cooler.  Set the temperature on the thermostat to 78 and then move air around the room or rooms you are using with an oscillating fan.  It’s an ideal way to maximize the benefits of central air conditioning.

Tip #5: Keep the Blinds Closed

Keeping blinds, shades and curtains closed during the day can help prevent sun from penetrating and heating up the house.  Some window treatments are available with thermal lining that does a great job of keeping heat out of your home.

Tip #6: Get Rid of Hot Air

Running the range vent will help remove warm air when you are cooking.  Running the bathroom vent will do the same during showers.  Getting rid of the humidity, which makes the house feel warmer, will be an added bonus.  Taking these steps will keep your central air conditioner from working harder than it needs to.

Tip #7: Save Work for Cooler Times of the Day

Do you have housework to do?  Schedule it for early morning or later in the day when possible, when the house is normally cooler because of lower outdoor temperatures.  You won’t get as warm doing chores and will be less inclined to lower the temperature on the thermostat to compensate.

Summary

High energy bills can cause us to lose our cool quickly.  These tips will help you keep your home and your utility bills at a comfortable level all season long.

Some of us enjoy a very cool indoor climate in summer; others just want to make it bearable.  Is there an optimal temperature to set the thermostat?  Personal preference aside, what is the best temperature to set the thermostat during air conditioning season?  This home HVAC guide takes a look at that, including the benefits involved.

Set your Thermostat for 78 Degrees for Air Conditioning

The truth is, if you want the most energy efficient setting, choose the highest temperature at which you are comfortable.  If that’s 78, that’s great.  If it’s 80, that’s even better.  Most home energy experts choose 78 degrees F as the “magic” temperature that should keep most homes comfortable without producing exceptionally high utility bills. An air conditioner running enough to maintain 78 degrees will also run long enough to remove plenty of humidity from your home.

Keep in mind that 78 degrees in air conditioning can be much more comfortable than 78 degrees outside.  First, you won’t be sitting in the sun while indoors, something that can make you very uncomfortable.  Secondly, air conditioners are like whole-house dehumidifiers.  They remove a large amount of humidity from the house.  We feel cooler at higher temperatures when there is less humidity. You may feel as comfortable with an air temperature of 78 or 80, with 40% humidity as you would at 72 or 74 degrees with 80% humidity.

Energy Savings with 78 Degrees

While the exact number varies based on the energy-efficiency of your air conditioner and the insulation qualities in your home, you can save between 15% to 25% on your energy use by setting the thermostat at 78 rather than 70 or 72. Factor 2-3% per degree.  That adds up significantly during the course of a long cooling season.

Other Ways to Reduce Energy Use while Air Conditioning

There are a few other things you can do to reduce energy use during the air conditioning season and still keep your home comfortable.  First, raise the temperature to 85 degrees when you’re gone.  Use a programmable thermostat to raise the temperature when you leave and lower it again shortly before you plan to get home. Secondly, use a low-constant fan setting on your furnace or air handler if it is equipped with one.  Trane’s Comfort-R system is one example.  The fan runs on low even when the AC isn’t running. This reduces humidity even more than the typical functioning of the air conditioner.

Thirdly, if you get a new central air conditioner, make sure it is sized correctly.  Most air conditioners are ½ ton to 1 ton too large.  When the AC is too large, it cools the house too quickly, not removing enough humidity in the process.  The result is a clammy feel in your home. You’ll have to turn down the thermostat even further to get the humidity control you want. Finally, set the thermostat and leave it alone.  Turning the thermostat down to 70 won’t cool off your house when it’s 85 any quicker than setting it to 78.  If you set it low, you run the risk of forgetting to adjust it upwards and wasting a lot of energy.  Use a programmable thermostat and then leave it alone as much as possible.

Summary

From a comfort standpoint, everyone is a bit different.  From an energy standpoint, setting the thermostat to 78 should help you stay comfortable while also keeping your warm weather utility bills under control.

While most homeowners don’t want to cool their homes down in winter, some consider running their central air conditioner in order to test the system.  They may be making repairs or demonstrating to a potential buyer that the system is working.  In addition, home appraisers working on loan applications are required to inspect the HVAC system. Will running an air conditioner in cold weather damage it?

Running the Air Conditioner in Cold Weather is Not Recommended

Air conditioning manufacturers and HVAC professionals agree, an outdoor condensing unit should not be run in cold weather for any reason.  The cause of this prohibition is the oil used to lubricate the compressor. There’s a significant amount of oil in the compressor and it functions like oil in your vehicle’s engine.

Just like engine oil, compressor oil for condensing units has different grades. The oil that is used in central air conditioner compressors is summer-weight oil.  It is a heavy grade of oil that works well in warm conditions.  It can heat up and still provide the compressor with the lubrication and protection required, something lighter grade of oil could not do.  In cold weather, the oil is too thick for the safe functioning of the compressor.

Safe Weather Temperatures for Running an Air Conditioner

Most HVAC technicians and home appraisers won’t run a central air conditioner unless daytime temperatures are above well above 60 degrees F for at least 2-3 days prior to the test.  That doesn’t leave much time of the year for testing in some parts of the country.  In many instances, the appraiser has to note that he or she did not test the AC unit, being prevented by whether conditions.  Most say that they have never been asked by a loan officer to go back later and test the unit.  Usually, a visual inspection of the condensing unit, along with running the gas furnace or air handler indoors, is enough to satisfy the underwriter for the loan.  Running the AC is not a make or break part of the process.

Air Conditioner Sensors Prevent Cold Weather Operation

Some newer AC units are now equipped with low-ambient temperature sensors that prevent the compressor from turning on in cooler weather, protecting the unit.  That’s another reason most home appraisers won’t even test in cool weather.  If the unit doesn’t come on, they can’t know if the condensing unit has mechanical issues or if it’s merely protecting itself against damage from unsafe operating conditions.

What About Heat Pumps?

Heat pumps run in cold weather, obviously.  The difference is that heat pump compressors are filled with a lighter grade of oil that performs in lower temperatures.

Summary

Keep this tip in mind if you are showing your home in cold weather to a prospective buyer.  Explain to them why you can’t run the condensing unit.  You may have to assure them that you’ll fix the AC if it doesn’t work once warm weather arrives, and you’ll probably need to include that in the purchase agreement.  It’s a better choice than running the condensing unit anyway and risking an expensive repair.

The major component of a central air conditioner system is known as the condensing unit.  It contains the compressor, the condensing coil, a fan and supporting parts.  Some homeowners wonder why it is placed there.  Why is a central air conditioner installed outside and not in the basement?  Let’s take a look.

How a Central Air Conditioner Works

Central air conditioning cools your home by removing heat from it.  The compressor pumps refrigerant into your home through a copper line.  The refrigerant enters an evaporator coil located inside the cabinet of your gas furnace, or in its own case mounted on your furnace.  In that indoor coil, the liquid refrigerant expands into a gas, rabidly absorbing heat in the process.  The result is that the indoor coil gets extremely cold.  The blower in the furnace circulates air over the coil, cooling it and pushing it into your home.  Removing heat, cooling the air, and cycling it through your home’s duct work outlines the basic process of central air conditioning.

But what happens to the heat?  The hot gas refrigerant travels through a second copper line to the condensing coil in the AC unit outside.  There, it is compressed back into a liquid.  In this process, the heat is squeezed out of it.  The condensing coil  has a surface on it that looks like a car radiator—or the outdoor side of a window AC unit.  The purpose for this is to allow the heat from the refrigerant to rapidly radiate out through the surface of the coil.  It is then dispersed by the condensing unit blower fan into the outside air.

Why a Central Air Conditioner is Installed Outside

It is probably clear to you by now why the condensing unit of the central air conditioner needs to be located outside. All of the heat being removed from your home by the circulating refrigerant gets left outside, creating cooler air inside.  If the condensing unit were located in your basement, it would have no way to discharge that heat from your home.

Conclusion

Central air conditioning is an amazing product of modern innovation and industry. When you choose your next central air conditioner, choose one with an efficiency level that works well for your climate – the warmer it is, the more efficient the AC should be.  Have a qualified contractor install it because only a properly installed air conditioner will run efficiently and be as free of mechanical problems as it should, giving you maximum service for the money.

This Top Rated Central Air Conditioners 2012 list gives you a starting point for finding the right model for your home.  You will find individual central air conditioner reviews for each of these models on this site, so you can research the ones you want to compare side by side.  Our criteria was not highest SEER rating as you can see.  Homeowners with different needs and purposes want different levels of efficiency.  For those in warmer climates or who want the greenest technology they can find, the higher the SEER the better. For cooler climates, a lower level of efficiency is more cost-effective.  It doesn’t make economic sense to pay 35-50% more to get a super-efficient AC you don’t use heavily.  Those in warm but not hot climates do best with something in between.

Our criteria for choosing the best central air conditioners for 2012 were quality and durability.  We picked models you can rely on to give you good performance for the greatest number of years.  That’s what value is – getting the maximum amount of service for the money you spend. By the way, all of these top rated central air conditioners are Energy Star qualified and they all use new, environmentally safer refrigerant. Here’s our list.

Top Rated Central Air Conditioners 2012

1. Maytag M1200 Series 24.5 SEER Central Air Conditioner

Energy Efficiency: 24.5 SEER

Maytag has made a concerted effort in recent years to lead the industry in efficiency and performance and this model demonstrates it. The heart of the unit is a modulating rotary compressor – something we’re seeing more of every year.  Rather than simply having low and high capacity, the compressor runs anywhere from 25% to 100% capacity, in 1% increments, to deliver just enough cooling at the moment to keep your home comfortable without a hint of temperature fluctuation.

This unit can be programmed to maintain humidity levels in your home between 35% and 70%, offers zoned cooling of up to 8 zones, and runs very quietly at lower capacities. This is at the top of the charts in terms of efficiency and one of the most expensive.

2. Carrier Infinity Series Model 24ANA1 Central Air Conditioner

Energy Efficiency 21 SEER

Carrier’s most efficient model features a 2-stage compressor for quieter, more balanced cooling than single-stage models can provide.  This is a very efficient AC that is suitable for hot summers. The Carrier Infinity controller is the top-rated model in the industry and allows for precise climate control in your home.

3. American Standard Platinum ZM Allegiance 20 Central Air Conditioner

Energy Efficiency: 20 SEER

American Standard has one of the highest consumer ratings for dependability, and this is their flagship model.  It runs at 50% capacity most of the time with the use of 2 high-quality Duration compressors, the second one kicking in for quick boosts in cooling when needed. The AccuLink communicating technology syncs system components for maximum efficiency and comfort, including temperature and humidity control. The fan is variable speed to reduce operating noise when running on low.

4. Amana Model ASXC18 18 SEER Central Air Conditioner

Energy Efficiency: 18 SEER

Amana may be the highest-quality AC manufacturer. This one uses the top-rated Copeland UtraTech scroll compressor and it is backed by a warranty that is easily the best in the industry.  If the compressor ever fails the original owners, Amana will replace the entire condensing unit. It’s a 2-stage model with all the features to keep it running reliably for many years.

5. Dave Lennox Signature Collection XC17 Central Air Conditioner

Energy Efficiency: 18 SEER

Part of Lennox’s top series, the XC 17 is an efficient, comfortable performer. It’s a single-stage compressor, the most efficient one on the market, which reduces the cost vs. 2-stage models, making it a good value. It offers very quiet performance and is compatible with Lennox’s humidity-reducing Humiditrol technology. The iComfort touchscreen thermostat is one of the highest-rated in the industry.

6. Trane High Efficiency XR15 Central Air Conditioner

Energy Efficiency: 17 SEER

This is another single-stage, very efficient AC.  The Trane ClimaTuff compressor does well in compressor ratings too, ensuring good durability and performance for this unit. The spine fin coil speeds up heat transfer for faster, more efficient cooling and the base pan is composite so won’t corrode.  This isn’t Trane’s most efficient air conditioner, but overall, the XR15 is their best.

7. Bryant Preferred Series Model 127A 16.5 SEER Central Air Conditioner

Energy Efficiency: 16.5 SEER

The Bryant Preferred Series is less efficient and less expensive than the Evolution Series but the same level of quality is present. The 2-stage compressor offers quieter performance that also produces better temperature balance without cool/warm zones in your home. This one has all the features like pressure switches and a refrigerant filter to ensure longevity and consistent performance through the years.

8. Heil QuietComfort Model Number DX 1600 Central Air Conditioner

Energy Efficiency: 16 SEER

This single-stage AC has a 2-speed fan for quieter operation.  It’s a good value, combining quality with a lower price point. The compressor insulation keeps down operating noise while the copper tube/aluminum fin coil allows for faster cooling of your home.

9. York Affinity Series Model CZE 15 SEER Central Air Conditioner

Energy Efficiency: 15 SEER

You won’t find many 15 SEER air conditioners with 2-stage compressors.  This model sells well in cooler climates where homeowners want the superior indoor comfort a 2-stage AC provides. With pressure switches and Comfort Alert technology, it’s a durable performer and one of the highest rated in its class.

10. Ruud UAPM-JEZ Series central air conditioner review Central Air Conditioner 14.5

Ruud makes quality models at many efficiency levels but this is one of their top models in overall ratings. It is a single-stage air conditioner with a reliable scroll compressor and a compressor blanket for quieter operation. Upgraded pressure switches, base pan and humidity control make it a top seller in cooler climates or for vacation homes and cabins.

Summary

Which of these top rated central air conditioners is right for you?  Consider your climate, your desire for green technology, your budget and how long you plan to remain in your home. These are all winners.  Remember to see our HVAC reviews on each of them for more complete details of the Top Rated Central Air Conditioners 2012.

Variable Speed Furnaces Deliver Balanced Cooling

Variable speed blowers work best in combination with 2-stage or modulating compressors in central air conditioners.  Staged operation provides more accurate cooling. The systems run at low capacity most of the time.  This prevents the central air conditioner from using too much energy to “over cool” your home.  Single-speed furnaces run too long at times, wasting energy when the home has already been cooled sufficiently during the cycle.  This can result in temperature fluctuations of 3-4 degrees versus 1-2 degrees with a variable speed furnace.  If you want the home to be 75 degrees, if the system cools it to 73 because it’s running on 100% capacity, that wastes energy and hurts the overall SEER ratio.

Variable Speed Furnaces Reduce Humidity More Effectively

A humid house is much harder to cool than one in which the humidity is being reduced by a variable-speed fan.  The harder it is to cool the house, the harder the air conditioner works and the less efficient it is.

It might help to understand how air conditioners reduce humidity in your home.  Inside your furnace is an evaporator coil, sometimes called an A coil because of its shape.  During a cooling cycle, refrigerant enters the coil and evaporates, capturing heat as it does so.  The refrigerant carries the heat out of the house and dumps it in the outside coil, called the condensing coil.

Inside the house, as heat is removed, the evaporator gets very cold.  As you know, humidity condenses on cold items like a cold glass of water.  As air from your home is passed over the coil by the furnace blower, humidity from the air condenses on the coil.  The A-shape of the coil allows moisture to run down it, enter a drain, and be removed from your home.  Air conditioners function something like a dehumidifier in this way.

Now, here’s how a variable speed furnace helps reduce humidity.  The variable-speed operation means the HVAC system runs for a longer period of time, with less cooling capacity, during each cycle.  The result is that the air from your home passes over the coil more often and more humidity is removed.   A variable speed furnace can remove up to 50% more humidity than a single speed furnace.

The less humid the air is, the easier it is to cool.  The air conditioner doesn’t work as hard so it is more efficient.  It’s that simple.

Summary

The most efficient air conditioner split systems features a 2-stage or modulating air conditioner with a variable speed furnace.  You’ll pay more for the system but the system will also pay you back more quickly.  You’ll use less energy and have lower utility bills.  As an added benefit, your home will be more comfortable.

We review many variable-speed furnaces as well as 2-stage and modulating air conditioners.  If home comfort and lower energy bills are your priorities, look for these models as you read our HVAC reviews on this site.  And when you choose your next system, have a qualified contractor install it.  Proper installation is a large part of having a system run as efficiently as possible from the start.

The top ten central air conditioners on the market offer a range of efficiency ratings so that you can choose the model that is right for your climate and needs.  In a hot and humid setting, a very high efficiency air conditioner will begin to pay for itself immediately through reduced electric bills.  In a cooler climate, a less efficient model will be more cost-effective when the lower equipment price is considered.  For vacation homes or those you plan to sell in the next few years, a quality, standard performance AC might make the most sense.

All of our choices for best central air conditioners are of the highest quality and they score very high in consumer and independent HVAC reviews.  That is our primary criterion. We list them in order of efficiency to make it easier to find the one that suits your purposes.  Here are the top ten central air conditioners in our overview.

1. Maytag M1200 Series 24.5 SEER Central Air Conditioner: 24.5 SEER.  This is the most efficient model we’ve reviewed and we don’t know of a split system central air conditioner with a higher SEER rating.  The key to its efficiency is the award-winning rotary compressor that offers 25% to 100% capacity, only delivering enough cooling to keep indoor temperatures comfortable with little fluctuation.  There won’t be any cold spots or warm spots when this unit is installed.  Maytag offers a 12-year warranty, better than most others.

2. American Standard Platinum ZM Allegiance 20 Central Air Conditioner: 20 SEER. This is the top of the line from one of the highest-rated manufacturers in the industry.  This unit has 2 compressors and operates at half power most of the time.  This enhances balanced cooling and improves removal of humidity from the air in your home.  The Duration compressors are durable and proven.  You can’t go wrong with Platinum Series model with the efficiency you need.

3. Trane Ultra Efficiency XL20i Central Air Conditioner: 20 SEER. Communicating technology protects the compressors and optimizes efficiency.  This model is similar to the one above.  It features 2 high-quality Climatuff compressors that offer gentler air conditioning but with enough power to quickly boost cooling and keep your home comfortable on the hottest days.  It will cost a bit more but deliver much more.

4. Carrier Infinity Series Model 24ANA1 Central Air Conditioner: 21 SEER. Carrier’s best deserves a spot near the top.  Staged cooling and high-quality component are the hallmark of this model.

5. Goodman 18 SEER R-410A Refrigerant – DSXC18 Central Air Conditioner: 18 SEER.  This model uses the top-rated compressor in the industry, the Copeland UltraTech scroll compressor.  It has the second-best warranty among the top ten air conditioners.  If features a lifetime limited compressor warranty that provides for replacement of the condensing unit if it fails in the first 10 years.

6. Amana Model ASXC18 18 SEER Central Air Conditioner: 18 SEER.  This AC is very similar to the Goodman listed above.  It takes the warranty one step further.  The compressor has a lifetime unit replacement warranty, giving you confidence from one of the industry’s top air conditioner brands.

7. Armstrong Model 418LE 18 SEER Central Air Conditioner: 18 SEER.  Armstrong is a brand that sometimes gets overlooked but it scores well in air conditioner performance ratings.  The Armstrong 418LE AC offers 2-stage cooling for maximized indoor comfort and should provide very good durability for many years.

8. Heil QuietComfort Model Number DX 1600 Central Air Conditioner: 16 SEER.  This single-stage AC offers quality and affordability.  That’s a combination that many homeowners are looking for.  It will also reduce electric costs in most homes when it replaces an older central air conditioner.

9. American Standard Platinum XM Allegiance 16 Central Air Conditioner: 16 SEER.  The Platinum Series is one of the top lines in the industry, so placing two from the Series on our list of the top ten air conditioners should be no surprise.  Two-stage cooling from a high-quality compressor is what you’ll get with this dynamic central air conditioner.

10. Ruud UAPM-JEZ Series Central Air Conditioner: 14.5 SEER. Ruud makes a range of central air conditioner models of the highest quality, giving you choices for good performance and durability no matter how efficient you need your AC to be.  This unit is built to last and will provide 15-20 years of reliable service.

Summary

All of these central air conditioners use R-410A refrigerant, or a variant of it, that is less harmful to the environment. Most of these are also Energy Star products.  If you choose a 2-stage air conditioner, you’ll get the best indoor performance if you match it with a variable-speed blower in the furnace or air handler. Whatever unit you choose, hire a qualified contractor to do the installation and you'll get the best performance and efficiency from it in the years ahead.   If you don’t want to sort through all the options to find the best, this list of the top ten air conditioners available does it for you and is a good place to begin.

The Green Guide To Air Conditioners 2011 looks at the growing interest in green technology, explains what’s available in terms of energy-efficient equipment and gives three examples of central air conditioners using green technology.  Consumer interest in energy-efficiency and reducing environmental impact has been growing, and it should be.

According to one national study, air conditioning can account for up to 50% of the country’s energy use during peak periods in summer.   It is estimated that more than 100 million tons of carbon dioxide emissions annually come from air conditioning.  In addition, old refrigerants are proven to be responsible for significant depletion of the earth’s ozone layer.

Not only is there an interest in energy-efficient central air conditioning, there is a significant demand that has driven manufacturers to produce models with a higher SEER rating.  SEER stands for Seasonal Energy Efficiency Rating and measures how efficiently the air conditioner uses electricity to cool air.  Each year, manufacturers add new, higher-efficiency models to their lineup and the average SEER ratings of their available products goes up.

Green Initiatives You can Take

So, what can you do to take a green approach to central air conditioning?

1. Look for High-Efficiency Models: To qualify as an Energy Star product, central air conditioners currently need to be rated at 14.5 SEER and 12 EER. This will almost certainly be increased in the next few years because the current minimum SEER allowed on the market is 13 while the most efficient residential central air conditioners are over 20 SEER. The higher the SEER rating you choose, the less energy the unit will consume and the fewer greenhouse gases will be produced in generating the electricity to run it.  To be as green as possible, choose the most efficient central air conditioner that meets your budget.

2. Choose R-410A Refrigerant: The newest refrigerant on the market, R-410A, does not contain chlorine and therefore does not deplete the earth’s ozone layer.  Most central air conditioners use it, but not all.  Carrier uses the brand name Puron and other brand names include Smart Cool 410.  The three models listed below all use the new, environmentally safer refrigerant.

3. Use a Programmable Thermostat: Turning your AC down when you are not at home, and still having a cool home when you get there, is easy with a programmable thermostat.  When you program the system to run less while you’re away, you can cut your energy use by 10% to 20%.

4. Make Sure the AC is Sized Correctly: Most AC installers oversize the system “just to be sure.”  That practice wastes energy.  If you are having a new central air conditioner installed, as you HVAC professional to do a load calculation to make sure the new system isn’t too big.

5. Choose a Qualified Contractor: It takes a skilled, experienced professional to install a unit and set it up properly so that it runs as efficiently as it should in the years ahead.

6. Clean your AC Consistently: When the coils found in the condensing unit or air handler get dirty, they lose efficiency.  Yard debris can accumulate on an outdoor coil. Dust can clog an indoor coil.  Hose off the outdoor coil after cutting the grass and have the indoor coil cleaned yearly to maintain peak efficiency.

Top Green Central Air Conditioners

If you are interested in the greenest central air conditioners on the market, these 3 are a good place to begin.

Maytag M1200 Series 24.5 SEER Central Air Conditioner

As you can see, this is a very efficient unit.  It’s one of the most efficient residential split-system air conditioners you can buy.  Many central air conditioners that are 12-20 years old are 6 SEER to 10 SEER models so it is easy to see how much more efficient this one is.  Replace an old model with it and you’ll cut your energy use and your greenhouse gas emissions by up to 75% when cooling your home.  The key to its efficiency is an innovative modulating compressor that can run as low as 25% capacity so it uses only the necessary energy to maintain consistent cooling.

Dave Lennox Signature Collection XC21 Central Air Conditioner

There are a couple of green innovations to note with the Lennox XC21.  First, the 21 SEER rating is outstanding, far in excess of Energy Star minimum standards.  It uses significantly less energy than most new central air conditioners on the market, reducing carbon emissions along with it.  Secondly, this AC is wired to accept the Lennox SunSource solar panels.  These PV solar panels can generate enough electricity to run the air conditioner – producing totally green energy. In some climates, the Lennox SunSource technology may produce enough extra energy to reduce the electrical load within your home.

Trane Ultra Efficiency XL20i Central Air Conditioner / American Standard Platinum ZM

These models are produced alongside each other by the same manufacturer and both offer 20 SEER air conditioning.  The key to their efficiency is that they each have 2 separate compressors, less powerful than a standard full-size compressor.  One compressor runs to maintain cooling and the second is employed only when a boost in cooling is demanded.  These energy-misers will reduce energy use by up to 60% in most homes.

Summary

When you combine a high-efficiency central air conditioner with energy-efficient practices in your daily routine, the result can be a very green approach to keep your home cool and comfortable during the summer.

Terms

Getting familiar with the terminology is an important part of an introduction to HVAC systems. We’ve listed the terms logically rather than in alphabetical order.

HVAC: This stands for Heating, Ventilation and Air Conditioning.

Condensing unit: The main component in a central air conditioner or heat pump.  It contains a compressor that pumps refrigerant, a condensing coil and a fan, along with supporting parts.

Refrigerant: A substance with the capacity to expand and absorb a significant amount of heat and then rapidly condense and shed that heat.  Refrigerant cools a home by absorbing and removing heat, and heats a home by absorbing heat outside and releasing it inside.  Refrigerant is used in both central air conditioners and in heat pump systems.

Heat pump: A condensing unit is usually associated with central air conditioning because it uses refrigerant to pull heat out of the home, thereby cooling the home.  A heat pump contains a condensing unit that also heats the home.  The flow of refrigerant is reversed.  Heat is captured outside and released by the refrigerant indoors.

Air handler: An HVAC component installed inside a building that pushes treated (heated or cooled) through the supply ducts and pulls untreated air into the system through the return ducts.  It does not produce heat.

Efficiency: This term refers to how efficiently the HVAC equipment uses its energy source to heat or cool air.  For condensing units, the efficiency is measured in SEER (Seasonal Energy Efficiency Rating) for air conditioning and HSPF (Heating Seasonal Performance Factor) for heating. In both cases, the higher the number is, the more efficient the unit is.  For gas and oil furnaces, efficiency is measured by AFUE (Annualized Fuel Use Efficiency), and is given in a percentage.  For example, in an 80% AFUE furnace, 80% of the heat created goes into the home and 20% is wasted in the venting process.  Today’s most efficient furnaces are more than 97% efficient.

Capacity: This is sometimes referred to as the “size” of a unit and refers to how much heating or air conditioned air a unit is capable of producing.  Condensing units are measured by tons, a reference to the cooling capacity of one ton of ice.  Residential condensing units are produced with capacities from 1.5 tons to 5.0 tons.  Their heating capacity is measure in Btuh, or British thermal units per hour.  One ton of cooling capacity is equal to approximately 12,000 Btuh.  Furnaces are measured by Btuh.

Types of HVAC Systems

This introduction to HVAC systems wouldn’t be complete without a discussion of the types of HVAC systems available.

Split system: An HVAC system in which a condensing unit or heat pump is installed outside the home and a furnace or air handler is installed inside.

Mini split system: An air conditioning system in which a small condensing unit is installed outside and up to 4 small evaporator units/air handlers are installed in rooms or zones.  These are also called ductless systems because they disperse air through the evaporator unit rather than through the building’s ductwork.  They are popular installations where no duct work exists.

Packaged Unit: Unlike a split system, both the heating and air conditioning components are housed in one large cabinet, installed outside the home or building.  There are several types of packaged units.  Gas packaged units, also called gas/electric packaged units or simply gas packs, use a furnace to heat and a condensing unit to cool.  Heat pump packaged units use a condensing unit to both heat and cool.  Air conditioner packaged units use a condensing unit to cool but have no source of heat.  They are used in residential settings where an alternate form of heating is used, and in commercial buildings in warm climates.

Keys to Cost

We’ll conclude this introduction to HVAC systems with a brief discussion of the major factors that affect cost.  In order of importance, they are:

1. Efficiency:  High-efficiency HVAC systems cost more for the equipment, but they use less energy and so produce reduced utility bills.  You’ll need to decide if purchasing high-efficiency equipment makes sense in your situation based on your area’s climate and how long you intend to stay in the home.

2. Capacity: The greater the volume of air that can be treated, the more the unit will cost, all else being equal.

3. Performance features: Certain features optimize the homeowner’s ability to precisely control indoor climate.  These include a 2-stage compressor in a condensing unit, multi-stage gas valve in a furnace, and a variable-speed blower in an air handler or gas furnace.  They are attractive to those who want very even temperatures with little fluctuation, but they also allow better humidity control in all seasons and better air filtration or purification.  This is primarily because they operate on low most of the time, and so they run more consistently.  Air circulates more continuously to achieve these desirable results.

Conclusion

While this introduction to HVAC systems isn’t exhaustive, it will give you the information you need to understand the basics of today’s heating and air conditioning systems.  The more information you have, the more likely you are to make decisions you’ll be satisfied with in the years to come.

This guide will help you match your needs to the best gas furnaces available.  If you live in a warm climate and don’t rely heavily on your furnace, a standard-efficiency model may serve your purposes.  If you live in a cold climate, then a high-efficiency model will pay for itself in 3-6 years by lowering energy bills.  If you enjoy precise climate control when heating or running an attached air conditioner, then a variable-speed blower is essential.  Also keep in mind your budget and the length of time you plan to live in the home when making your purchasing decision.  These are the factors that will help you select the gas furnace for you.  This Top Rated Gas Furnaces 2011 Guide will point you in the right direction.

Standard Efficiency Furnaces: 80% AFUE

High Efficiency Furnaces: 90% to 95% AFUE

Very High Efficiency Furnaces: Above 95% AFUE

AFUE stands for Annualized Fuel Efficiency and gives the percentage of created heat that actually goes into your home.  An 80% AFUE furnace will lose 20% of its heat out the flue; a 95% AFUE furnace will lose just 5%.  Prices tend to follow the AFUE rating, with the most efficient furnaces costing the most, primarily because they have a secondary heat exchanger to capture more heat.  Keep in mind, of course, that the higher the efficiency, the lower your energy costs will be.

Top Very High Efficiency Gas Furnaces

1. Dave Lennox Signature Collection SLP98V Variable-Capacity Gas Furnace

Lennox has long been one of the leading brands in the HVAC industry and products like the Dave Lennox Signature Collection SLP98V Variable-Capacity Gas Furnace keep them at or near the top.  This is Lennox’s best all-around furnace, combining ultra-high 98.2% AFUE with a variable-speed blower for enhanced comfort in every season.

Top Features of the Dave Lennox Signature Collection SLP98V Variable-Capacity Gas Furnace

Besides very high efficiency, this flagship furnace offers PerfectHeat 2-stage operation and PerfectHumidity control, systems that produce balanced heating and air conditioning with better humidity control and air filtration.

Who Should Consider the Dave Lennox Signature Collection SLP98V Gas Furnace?

Homeowners in cooler climates who expect a lot from their gas furnace will get it with this Lennox.  It’s built to produce greater year-round comfort in any home.  This is also attractive for anyone who wants to reduce carbon emissions with a very high-efficiency gas furnace.

Other Top Very High Efficiency Furnaces to Compare and Consider

2. Bryant Evolution Series Plus 90i Gas Furnace

Bryant quality is found throughout this gas furnace that achieves 96.6% efficiency.  Two heat exchangers capture more heat and reduce energy consumption.  2-stage heating and the FanOnPlus produce unsurpassed indoor comfort.

3. York Affinity Series Model 9.C Gas Furnace

York is known for making HVAC products that are packed with leading edge technology and the most efficient components in the industry.  This York gas furnace offers outstanding 98% AFUE with a modulating gas burner that rises in 1% increments and a variable-speed blower.  It offers the most precise temperature control you can find from a gas furnace today.  It’s expensive, but for those who want a furnace that can produce the finest indoor climate, this model should be considered.

4. Trane Two-Stage XV95 Gas Furnace

This well-designed Trane furnace delivers up to 96.7% AFUE which is sure to lower energy bills in your home.  The 2-stage burner is an energy-miser and assists the variable-speed blower in tailoring your home’s climate to your exact specifications.  The aluminized heat exchanger is efficient and very durable.

Top High Efficiency Gas Furnaces

1. Goodman Multi-Position, Variable Speed, 95% AFUE — GMVC95 Gas Furnace

Goodman has built a very credible reputation by offering high-quality products that perform very well.  This one meets those criterion, plus it is backed by one of the best warranties in the business and has a very affordable price.

Top Features of the Goodman GMVC95 Gas Furnace

This Energy Star furnace uses a 2-stage gas valve that conserves energy when the heat in the home is being maintained.  It opens fully when a boost in heat is called for.  The variable-speed motor enhances climate control when heating or when used with a central air conditioner.  At 95% efficiency, just 5% of heat is lost.  There’s a lifetime limited warranty on the heat exchanger and a 10-year limited warranty on all other parts.

Who Should Consider the Goodman GMVC95 Gas Furnace?

This is a very good choice in moderate to cold climates where a workhorse furnace is required.  It has the quality components for heavy use and the fuel efficiency that will reduce energy costs dramatically when it replaces an older gas furnace.  The price of this gas furnace also makes it a good value.

Other Top High Efficiency Gas Furnaces to Compare and Consider

2. Lennox Merit Series ML193 Gas Furnace

Another Energy Star furnace, this one offers 93% AFUE and a stainless steel heat exchanger for excellent durability.  This is Lennox’s base model, and its’ high efficiency comes at an excellent price.  It comes with a 20-year limited heat exchanger warranty and 5 years on everything else.

3. Aire Flo CG95 Model CG95TB040D12B Gas Furnace

The 95% efficiency will reduce heating bills by as much as 35% or more in many homes.  The aluminized steel heat exchanger and durable hot surface igniter are built for durability.  The variable-speed blower offers excellent indoor comfort in all seasons.

4. Carrier Comfort 92 Gas Furnace

This gas furnace is what you expect from a Carrier – reliable, efficient, and quiet and backed by a very good warranty.  The SerpenTuff heat exchanger transfers up to 95% of the created heat into your home, producing reduced energy costs.  The ComfortFan technology reduces operating noise while delivering better air flow.

Top Standard Efficiency Gas Furnaces

1. Amana AMH8 TwinComfort, Multi-Speed Gas Furnace

This 80% AFUE gas furnace delivers a good blend of standard efficiency and performance features that will help make your home more comfortable when heating or using with a central air conditioner.  Amana also does a great job making their quality gas furnaces affordable to their customers.  Let’s take a closer look.

Top Features of the Amana AMH8 TwinComfort, Multi-Speed Gas Furnace

Performance begins with a 2-stage gas valve and a multi-stage blower that starts slow to prevent initial blasts of untreated air.  You won’t get a stream of cool air while waiting for the furnace to heat up.  The patented tubular MillionAir heat exchanger is crafted from stainless steel to optimize heat transfer and minimize wear and corrosion.  The multi-speed blower and the Auto-comfort mode will help you control indoor climate in all seasons.  The Amana AMH8 TwinComfort gas furnace is backed by a very good warranty.  Amana will replace the furnace if the heat exchanger fails in the first 10 years.  The heat exchanger is covered with a limited lifetime warranty and all other parts have a 10-year limited warranty.

Who Should Consider the Amana AMH8 TwinComfort, Multi-Speed Gas Furnace?

This is an ideal gas furnace for homeowners in warmer climates who want precise control over indoor climate but don’t need a high-efficiency furnace.  It has a lower price tag than a high or very high efficiency furnace yet is equipped with a variable-speed blower that helps balance heating and air conditioning as well as providing enhanced humidity control and better air quality.

Other Top Standard Efficiency Gas Furnaces to Compare and Consider

2. American Standard Silver XI Freedom 80 High Efficiency Single Stage Furnace

This furnace has a single-stage gas valve for lower equipment costs and a variable-speed blower for better climate control.  American Standard has a very good service record and their units do well in gas furnace reviews.  A 10-year limited warranty covers everything.

3. Rheem Classic Plus Series Super Quiet 80 Downflow RGLT Gas Furnace

This is a very good choice for attic installation.  It features a patented heat exchanger made from aluminized steel that resists corrosion while effectively transferring heat.  The low-profile, compact design makes installation much easier.

4. Goodman Multi-Position — GME8 Gas Furnace

This durable gas furnace has a 2-stage gas valve for quiet, efficient heating.  The dual-diameter heat exchanger offers excellent durability and is backed by a lifetime limited warranty, including furnace replacement if it fails in the first 10 years.  This is a rock-solid, reliable furnace.

Conclusion

Which gas furnace is right for you?  Use the factors we discussed above to pick out several to compare and consider.  And when you do find the best gas furnace for your home, it makes sense to have an HVAC professional install it.  Only a qualified contractor has the training, skill, and the daily experience to install and tune your furnace and other HVAC components.  Proper installation is a major key to getting top performance and longevity from the furnace you choose for your home.