Ventilation Systems for Cooling

Ventilation is the least expensive and most energy-efficient way to cool buildings. Ventilation works best when combined with methods to avoid heat buildup in your home. In some cases, natural ventilation will suffice for cooling, although it usually needs to be supplemented with spot ventilation, ceiling fans, and window fans. For large homes, homeowners might want to investigate whole house fans.

Interior ventilation is ineffective in hot, humid climates where temperature swings between day and night are small. In these climates, natural ventilation of your attic (often required by building codes) will help to reduce your use of air conditioning, and attic fans may also prove beneficial. However, an alternate approach is to seal the attic and make it part of the conditioned space in your house, putting the insulation on the inside of the roof rather than on the floor of the attic. Sealed attics are more feasible in new home construction, but can be retrofitted on an existing house.

Principles of Heating and Cooling

Understanding the roles of conduction, convection, radiation, and perspiration.

Avoiding Heat Buildup

Keeping the outside heat outside, avoiding heat-generating activities, and using spot ventilation can help keep your home cool during hot days.

To avoid heat buildup in your home, plan ahead by landscaping your lot to shade your house. If you replace your roof, use a light-colored material to help it reflect heat. Insulate your house to at least the recommended levels to help keep out the heat, and consider using a radiant barrier.

On hot days, whenever outdoor temperatures are higher than the temperature inside your house, close tightly all the windows and exterior doors. Also install window shades or other window treatments and close the shades. Shades will help block out not only direct sunlight, but also radiated heat from the outdoors, and insulated shades will reduce the conduction of heat into your home through your windows.

Cooking can be a major source of heat within a home. On hot days, avoid using the oven; cook on the stovetop, or better yet, use only a microwave oven. For stovetop or oven cooking, use the spot ventilation of your oven hood to help remove the heat from the house (this will suck some hot outside air into your home, so don't overdo it). Outdoor grilling is a great way to avoid cooking indoors, and of course, going out to eat or ordering take-out work as well.

Bathing, washing laundry, and other activities can also pump heat into your home. When you shower or take a bath, use the spot ventilation of a bathroom fan to remove the heat and humidity from your home. Your laundry room might also benefit from spot ventilation. If you use an electric dryer, be sure it's vented to the outside (for safety, gas dryers should ALWAYS be vented to the outside). If you live in an older home with a sump that your laundry drains to, drain the sump after running any loads in hot water (or better yet, avoid using hot water for your laundry).

Finally, avoid any activities that generate a lot of heat, such as running a computer, burning open flames, running a dishwasher, and using hot devices such as curling irons or hair dryers. Even stereos and televisions will add some heat to your home.

Natural Ventilation

In some parts of the United States, natural convection and cool breezes are sufficient to keep homes cool.

Ceiling Fans, Window Fans, and Other Circulating Fans

Fans that circulate air within your home can improve your comfort level. Window fans use relatively little electricity and provide sufficient cooling for homes in many parts of the country.

Whole House Fans

For larger homes, a whole house fan provides excellent ventilation to achieve lower indoor temperatures. For homes with ducts, an alternative approach uses those ducts to supply ventilation air throughout the home.



Maintaining Your Air Conditioner

An air conditioner's filters, coils, and fins require regular maintenance for the unit to function effectively and efficiently throughout its years of service. Neglecting necessary maintenance ensures a steady decline in air conditioning performance while energy use steadily increases. Check out our Energy Saver 101 Infographic: Home Cooling for more ways to help improve your comfort and the efficiency of your air conditioner.

Air Conditioner Filters

The most important maintenance task that will ensure the efficiency of your air conditioner is to routinely replace or clean its filters. Clogged, dirty filters block normal airflow and reduce a system's efficiency significantly. With normal airflow obstructed, air that bypasses the filter may carry dirt directly into the evaporator coil and impair the coil's heat-absorbing capacity. Replacing a dirty, clogged filter with a clean one can lower your air conditioner's energy consumption by 5% to 15%.

For central air conditioners, filters are generally located somewhere along the return duct's length. Common filter locations are in walls, ceilings, furnaces, or in the air conditioner itself. Room air conditioners have a filter mounted in the grill that faces into the room.

Some types of filters are reusable; others must be replaced. They are available in a variety of types and efficiencies. Clean or replace your air conditioning system's filter or filters every month or two during the cooling season. Filters may need more frequent attention if the air conditioner is in constant use, is subjected to dusty conditions, or you have fur-bearing pets in the house.

Air Conditioner Coils

The air conditioner's evaporator coil and condenser coil collect dirt over their months and years of service. A clean filter prevents the evaporator coil from soiling quickly. In time, however, the evaporator coil will still collect dirt. This dirt reduces airflow and insulates the coil, reducing its ability to absorb heat. To avoid this problem, check your evaporator coil every year and clean it as necessary.

Outdoor condenser coils can also become very dirty if the outdoor environment is dusty or if there is foliage nearby. You can easily see the condenser coil and notice if dirt is collecting on its fins.

You should minimize dirt and debris near the condenser unit. Your dryer vents, falling leaves, and lawn mower are all potential sources of dirt and debris. Cleaning the area around the coil, removing any debris, and trimming foliage back at least 2 feet (0.6 meters) allow for adequate airflow around the condenser.

Coil Fins

The aluminum fins on evaporator and condenser coils are easily bent and can block airflow through the coil. Air conditioning wholesalers sell a tool called a "fin comb" that will comb these fins back into nearly original condition.

Condensate Drains

Occasionally pass a stiff wire through the unit's drain channels. Clogged drain channels prevent a unit from reducing humidity, and the resulting excess moisture may discolor walls or carpet.

Window Seals for Room Air Conditioners

At the start of each cooling season, inspect the seal between the air conditioner and the window frame to ensure it makes contact with the unit's metal case. Moisture can damage this seal, allowing cool air to escape from your house.

Preparing for Winter

In the winter, either cover your room air conditioner or remove and store it. Covering the outdoor unit of a central air conditioner will protect the unit from winter weather and debris.

Hiring a Professional

When your air conditioner needs more than regular maintenance, hire a professional service technician. A well-trained technician will find and fix problems in your air conditioning system.

The technician should:

  • Check for correct amount of refrigerant
  • Test for refrigerant leaks using a leak detector
  • Capture any refrigerant that must be evacuated from the system, instead of illegally releasing it to the atmosphere
  • Check for and seal duct leakage in central systems
  • Measure airflow through the evaporator coil
  • Verify the correct electric control sequence and make sure that the heating system and cooling system cannot operate simultaneously
  • Inspect electric terminals, clean and tighten connections, and apply a non-conductive coating if necessary
  • Oil motors and check belts for tightness and wear
  • Check the accuracy of the thermostat.



Tips: Heating and Cooling

Heating and cooling your home uses more energy and costs more money than any other system in your home -- typically making up about 48% of your utility bill.

No matter what kind of heating and cooling system you have in your house, you can save money and increase your comfort by properly maintaining and upgrading your equipment. But remember, an energy-efficient furnace alone will not have as great an impact on your energy bills as using the whole-house approach. By combining proper equipment maintenance and upgrades with recommended insulation, air sealing, and thermostat settings, you can save about 30% on your energy bill while reducing environmental emissions.

Heating and Cooling Tips

  • Set your programmable thermostat as low as is comfortable in the winter and as high as is comfortable in the summer, and -- depending on the season -- raise or lower the setpoint when you're sleeping or away from home.
  • Clean or replace filters on furnaces and air conditioners once a month or as recommended.
  • Clean warm-air registers, baseboard heaters, and radiators as needed; make sure they're not blocked by furniture, carpeting, or drapes.
  • Eliminate trapped air from hot-water radiators once or twice a season; if unsure about how to perform this task, contact a professional.
  • Place heat-resistant radiator reflectors between exterior walls and the radiators.
  • Turn off kitchen, bath, and other exhaust fans within 20 minutes after you are done cooking or bathing; when replacing exhaust fans, consider installing high-efficiency, low-noise models.
  • During winter, keep the draperies and shades on your south-facing windows open during the day to allow the sunlight to enter your home and closed at night to reduce the chill you may feel from cold windows.
  • During summer, keep the window coverings closed during the day to block the sun's heat.

Long-Term Savings Tips

  • Select energy-efficient products when you buy new heating and cooling equipment. Your contractor should be able to give you energy fact sheets for different types, models, and designs to help you compare energy usage.
  • For furnaces, look for high Annual Fuel Utilization Efficiency (AFUE) ratings. The national minimum is 78% AFUE, but there are ENERGY STAR® models on the market that exceed 90% AFUE. For air conditioners, look for a high Seasonal Energy Efficiency Ratio (SEER). The current minimum is 13 SEER for central air conditioners. ENERGY STAR models are 14.5 SEER or more.



Living Comfortably: A Consumer’s Guide to Home Energy Upgrades

A comfortable home is an energy-efficient home. The steps below outline the process for making your home more comfortable through energy upgrades and highlight the importance of choosing certified home energy professionals to do the work.

Step 1: Start with the Right Contractor

Not all contractors are the same. Some concentrate on kitchens, some on bathrooms. Some concentrate on home energy upgrades -- focusing on ways to make your home comfortable, energy efficient and healthy. Look for companies that employ workers who carry the national Home Energy Professional Certifications. A home performance contractor will have a certified auditor either on staff or under contract to evaluate your home.

Step 2: Get a Thorough Home Energy Audit

A home performance evaluation, or energy audit, requires specialized equipment and trained individuals -- called energy auditors -- to operate that equipment. Energy auditors who carry a Home Energy Professional Certification have met the required professional and educational prerequisites and are certified to the highest standard in the industry, proving they are qualified to conduct a home performance evaluation.

The most important piece of equipment an energy auditor operates is called a blower door, which is used to determine where air is leaking out of your home. If you followed the auditor around while the blower door is running, you might be surprised at what you’d find. Air leaking through face plates on switches and outlets, and escaping around doors, windows, pipes, and under sinks … and all of these places add up. Put them all together and you could have a space the size of a bathroom window -- maybe even bigger -- that’s constantly open. The blower door test is a good way to learn why your house isn’t comfortable.

In addition to the blower door, certified energy auditors use tools -- such as gas leak detectors, carbon monoxide detectors, kill-a-watt meters and lead-safe testing kits -- to give your home a thorough evaluation.

Be sure to ask if your auditor is certified and what equipment will be used for the evaluation. If your auditor is just going to walk through your house and estimate what work needs to be done, you don’t have an experienced home performance contractor. Ask if you can shadow the auditor during the evaluation -- most will welcome the chance to teach you about your home.

Step 3: Ask the Right Questions

While all homes are different and need to be evaluated based on their own unique characteristics, most dwellings can benefit from similar types of improvements. Before your energy audit begins, be sure to ask your home energy upgrade contractor about the following things. Some of the upgrades you could do yourself, like replacing a refrigerator or installing a programmable thermostat, provided you know those are significant sources of energy loss.

Air Sealing

Remember that space in your house that’s the size of a bathroom window and constantly open? Using the reading from the blower door, an auditor can figure out just how much air is moving through that gap at any given time. This is usually the biggest source of energy loss in a home, and sealing those gaps is one of the quickest ways to make your home more comfortable and efficient. Reducing air flow can pay off in as little as five years. It is also the baseline by which all other energy efficiency upgrades are measured (the absolute energy savings will vary by your climate). Read more about air sealing.

Reset Water Heater Thermostat

Most water heaters heat water to a set temperature and then hold it there. This means that all day and night, the water heater cycles on and off, just maintaining that set temperature. Lowering the setting a few degrees can often save half as much energy as air sealing would. And chances are turning down the temperature won’t even be noticeable. Read more tips for efficient water heating.

Programmable Thermostat for Heating System

It seems obvious but just like the water heater maintains a set temperature even when it isn’t being used, a thermostat does the same thing for the entire house. Just letting it cool off (or warm up) when there isn’t anyone awake can save energy and money as well. Without sacrificing comfort, it can also be close to half of what air sealing would save you. This change usually pays for itself in about three years.

Attic and Wall Insulation

The greater the difference between the indoor and the outdoor temperatures, the more energy it will take to maintain a comfortable temperature in your home. Adding insulation between the indoors and the outdoors reduces that energy demand. Depending on where you live, the savings from insulating your walls and the attic could be almost double the savings of air sealing. This procedure also pays back in 3 1/2 to 12 years. Learn how to estimate the payback period of insulation.

Replace Refrigerator

Much like a water heater, a refrigerator holds a set temperature that is very different from the air outside of it. It makes sense that a better sealed, better insulated refrigerator with better mechanical systems would save more energy. Depending on your previous model, a new ENERGY STAR® refrigerator can save up to $150 per year. One way to test the seal on your refrigerator is to close a dollar bill in the door. If the bill drops when you close the door, you may want to consider fixing the seal or getting a new one. Depending on the refrigerator and the savings, this can pay for itself in 10 years -- well under the average lifespan of the appliance.

Water Heaters and Furnaces

The savings from water heaters and furnaces depend a lot on where the house is and what the fuel is. Generally, natural gas is going to be much cheaper than electricity, provided it’s available. The newer high efficiency gas furnaces will often be worth installing, even if the gas furnace in your home is relatively new. Depending on if you live in a cold climate or a warmer one, a new high efficiency furnace will rival or exceed air sealing for its potential savings. In warmer areas, a high efficiency heat pump may replace a gas furnace as the best choice for the home.

Step 4: Enjoy

In the end, your home is as unique as you are. It will take a certified home energy professional to evaluate your home and your family’s specific needs. It will also take a certified specialist to make those upgrades to your home. It’s not rocket science, but it is building science. Ask for certified home energy professionals because they have the ability to educate you on all of the cost-saving alternatives for your home. Then, you can begin living comfortably.

The U.S. Department of Energy, with support from its National Renewable Energy Laboratory and the Building Performance Institute, Inc., recently concluded its pilot testing period for the new Home Energy Professional Certifications. The purpose of the pilot testing period is to scrutinize and evaluate the proposed exam questions, practical/field components, and overall exam processes prior to achieving American National Standards Institute (ANSI) accreditation. ANSI accreditation indicates high quality and diligence. After the accreditation process is completed, the new Home Energy Professional Certification exams will be available at a national level. Interested individuals should visit the Building Performance Institute, Inc. website for more details.

Energy audit tools

  • An infrared camera can display temperature differences between surfaces and help determine if a wall is insulated. It can show drafts and moisture, which can lead to mold problems.
  • A carbon monoxide meter is used to determine if your combustion appliances are properly vented so the air is safe for your family to breathe.
  • A blower door is used to measure leakage in air ducts, which affects heating and cooling efficiency.

What does this mean for me?

An energy audit conducted by a certified home energy professional auditor can ensure that your home is as comfortable and energy efficient as possible.



Heat & Cool Efficiently

As much as half of the energy used in your home goes to heating and cooling. So making smart decisions about your home's heating, ventilating, and air conditioning (HVAC) system can have a big effect on your utility bills — and your comfort. Take these steps to increase the efficiency of your heating and cooling system. For more information, see our Guide to Energy Efficient Heating & Cooling (708KB).

Change your air filter regularly

Check your filter every month, especially during heavy use months (winter and summer). If the filter looks dirty after a month, change it. At a minimum, change the filter every 3 months. A dirty filter will slow down air flow and make the system work harder to keep you warm or cool — wasting energy. A clean filter will also prevent dust and dirt from building up in the system — leading to expensive maintenance and/or early system failure.

Tune up your HVAC equipment yearly

Just as a tune-up for your car can improve your gas mileage, a yearly tune-up of your heating and cooling system can improve efficiency and comfort. Learn more:

Install a programmable thermostat

A programmable thermostat is ideal for people who are away from home during set periods of time throughout the week. Through proper use of pre-programmed settings, a programmable thermostat can save you about $180 every year in energy costs.

Seal your heating and cooling ducts

Ducts that move air to-and-from a forced air furnace, central air conditioner, or heat pump are often big energy wasters. Sealing and insulating ducts can improve the efficiency of your heating and cooling system by as much as 20 percent — and sometimes much more.

Focus first on sealing ducts that run through the attic, crawlspace, unheated basement, or garage. Use duct sealant (mastic) or metal-backed (foil) tape to seal the seams and connections of ducts. After sealing the ducts in those spaces, wrap them in insulation to keep them from getting hot in the summer or cold in the winter. Next, look to seal any other ducts that you can access in the heated or cooled part of the house. See our See our Duct Sealing brochure (1.13MB) for more information. for more information.

Consider installing ENERGY STAR qualified heating and cooling equipment

If your HVAC equipment is more than 10 years old or not keeping your house comfortable, have it evaluated by a professional HVAC contractor. If it is not performing efficiently or needs upgrading, consider replacing it with a unit that has earned the ENERGY STAR. Depending on where you live, replacing your old heating and cooling equipment with ENERGY STAR qualified equipment can cut your annual energy bill by more than $115. But before you invest in a new HVAC system, make sure that you have addressed the big air leaks in your house and the duct system. Sometimes, these are the real sources of problems rather than your HVAC equipment.

Ask about Proper Installation of your new equipment

Replacing your old heating and cooling equipment with new, energy-efficient models is a great start. But to make sure that you get the best performance, the new equipment must be properly installed. In fact, improper installation can reduce system efficiency by up to 30 percent - costing you more on your utility bills and possibly shortening the equipment's life. Learn more.



How to Read Residential Electric and Natural Gas Meters

You can read your own meters to help monitor your electric or gas energy use. During the heating season, your energy use should be compared to the number of heating degree days for the same time period; during the cooling season, compare your energy use to the number of cooling degree days.

Heating and cooling degree days are a simple measure of the effect of weather on your energy needs: using the average temperature for each day, each degree Fahrenheit below 65°F is counted as one heating degree day, and each degree Fahrenheit above 65°F is counted as one cooling degree day. Your heating and cooling use should be proportional to the number of heating and cooling degree days for the time period in question.

You may also wish to contact your local utility companies for more information about reading your meter. If monthly information is good enough, your utility bills could have all the information you need. Just be sure the bills are based on actual, not estimated, meter readings, and be aware of when the meter was read, because the time period between readings can vary. Contact your local utility if you are uncertain about this.

Electric Meters

The basic unit of measure of electric power is the watt. One thousand watts are called a kilowatt. If you use one thousand watts of power in one hour you have used a kilowatt-hour (kWh). Your electric utility bills you by the kWh.

The standard electric power meter is a clock-like device driven by the electricity moving through it. As the home draws current from the power lines, a set of small gears inside the meter move. The number of revolutions is recorded by the dials that you can see on the face of the meter. The speed of the revolutions depends on the amount of current drawn -- the more power consumed at any one instant, the faster the gears will rotate.

When reading an electric meter, read and write down the numbers as shown on the dials from right to left. When the pointer is directly on a number, look at the dial to the right. If it has passed zero, use the next higher number. If it has not passed zero, use the lower number. Record the numbers shown by writing down the value of the dial to your extreme right first and the rest as you come to them. Should the hand of a dial fall between two numbers, use the smaller of the two numbers.

Natural Gas Meters

Natural gas is commonly measured by the cubic foot, and you are billed by the thousands of cubic feet (MCF) or hundreds of cubic feet (CCF). You may also be billed by the therm, which is about the same as a CCF or 100 cubic feet. To measure the amount of electricity or gas that you use, the utility installs a meter between the incoming electric power or gas lines and the point of distribution at the house.

A gas meter is driven by the force of the moving gas in the pipe, and also turns faster as the flow increases. Each time the dial with the lower value makes one complete revolution, the pointer on the next higher value dial moves ahead one digit.

When reading a gas meter, read and write down the numbers as shown on the dials from left to right (opposite of an electric meter). It is important to note that on both types of meters, the hands of adjacent dials turn in opposite directions to each other.

Digital Meters

Note that some newer electric and gas meters use digital displays instead of dials. The difference between one month's reading and the next is the amount of energy units that have been used for that billing period.




You can save money on your heating and cooling bills by simply resetting your thermostat when you are asleep or away from home. You can do this automatically without sacrificing comfort by installing an automatic setback or programmable thermostat.

Using a programmable thermostat, you can adjust the times you turn on the heating or air-conditioning according to a pre-set schedule. Programmable thermostats can store and repeat multiple daily settings (six or more temperature settings a day) that you can manually override without affecting the rest of the daily or weekly program.

General Thermostat Operation

You can easily save energy in the winter by setting the thermostat to 68°F while you're awake and setting it lower while you're asleep or away from home. By turning your thermostat back 10° to 15° for 8 hours, you can save 5% to 15% a year on your heating bill -- a savings of as much as 1% for each degree if the setback period is eight hours long. The percentage of savings from setback is greater for buildings in milder climates than for those in more severe climates.

In the summer, you can follow the same strategy with central air conditioning by keeping your house warmer than normal when you are away, and setting the thermostat to 78°F (26°C) only when you are at home and need cooling. Although thermostats can be adjusted manually, programmable thermostats will avoid any discomfort by returning temperatures to normal before you wake or return home.

A common misconception associated with thermostats is that a furnace works harder than normal to warm the space back to a comfortable temperature after the thermostat has been set back, resulting in little or no savings. In fact, as soon as your house drops below its normal temperature, it will lose energy to the surrounding environment more slowly. The lower the interior temperature, the slower the heat loss. So the longer your house remains at the lower temperature, the more energy you save, because your house has lost less energy than it would have at the higher temperature. The same concept applies to raising your thermostat setting in the summer -- a higher interior temperature will slow the flow of heat into your house, saving energy on air conditioning. Check out our home heating infographic to learn more about how heating systems and thermostats interact.

Limitations for Homes With Heat Pumps, Electric Resistance Heating, Steam Heat, and Radiant Floor Heating

Programmable thermostats are generally not recommended for heat pumps. In its cooling mode, a heat pump operates like an air conditioner, so turning up the thermostat (either manually or with a programmable thermostat) will save energy and money. But when a heat pump is in its heating mode, setting back its thermostat can cause the unit to operate inefficiently, thereby canceling out any savings achieved by lowering the temperature setting. Maintaining a moderate setting is the most cost-effective practice. Recently, however, some companies have begun selling specially designed programmable thermostats for heat pumps, which make setting back the thermostat cost-effective. These thermostats typically use special algorithms to minimize the use of backup electric resistance heat systems.

Electric resistance systems, such as electric baseboard heating, require thermostats capable of directly controlling 120-volt or 240-volt circuits. Only a few companies manufacture line-voltage programmable thermostats.

The slow response time -- up to several hours -- of steam heating and radiant floor heating systems leads some people to suggest that setback is inappropriate for these systems. However, some manufacturers now offer thermostats that track the performance of your heating system to determine when to turn it on in order to achieve comfortable temperatures at your programmed time.

Alternately, a normal programmable thermostat can be set to begin its cool down well before you leave or go to bed and return to its regular temperature two or three hours before you wake up or return home. This may require some guesswork at first, but with a little trial and error you can still save energy while maintaining a comfortable home.

Choosing and Programming a Programmable Thermostat

Most programmable thermostats are either digital, electromechanical, or some mixture of the two. Digital thermostats offer the most features in terms of multiple setback settings, overrides, and adjustments for daylight savings time, but may be difficult for some people to program. Electromechanical systems often involve pegs or sliding bars and are relatively simple to program.

When programming your thermostat, consider when you normally go to sleep and wake up. If you prefer to sleep at a cooler temperature during the winter, you might want to start the temperature setback a bit ahead of the time you actually go to bed. Also consider the schedules of everyone in the household. If there is a time during the day when the house is unoccupied for four hours or more, it makes sense to adjust the temperature during those periods.

Other Considerations

The location of your thermostat can affect its performance and efficiency. Read the manufacturer's installation instructions to prevent "ghost readings" or unnecessary furnace or air conditioner cycling. To operate properly, a thermostat must be on an interior wall away from direct sunlight, drafts, doorways, skylights, and windows. It should be located where natural room air currents–warm air rising, cool air sinking–occur. Furniture will block natural air movement, so do not place pieces in front of or below your thermostat. Also make sure your thermostat is conveniently located for programming.



Why Seal and Insulate?

Save Energy and Money.

Air that leaks through your home's envelope − the outer walls, windows, doors, and other openings − wastes a lot of energy and increases your utility costs. A well-sealed envelope, coupled with the right amount of insulation, can make a real difference on your utility bills.

Increase Comfort.

Sealing leaks and adding insulation can improve the overall comfort of your home and help to fix many of these common problems:

  • Reduced noise from outside
  • Less pollen, dust and insects (or pests) entering your home
  • Better humidity control
  • Lower chance for ice dams on the roof/eves in snowy climates

Most Homes Will Benefit.

Most homes in the United States don't have enough insulation and have significant air leaks. In fact, if you added up all the leaks, holes and gaps in a typical home's envelope, it would be the equivalent of having a window open every day of the year!



Energy Saver 101 Infographic: Home Cooling

As summer starts to heat up and temperatures rise, many of us are cranking up the air conditioners to stay cool. It should come as no surprise then that air conditioners use about 5 percent of all the electricity produced in the U.S., costing homeowners more than $11 billion a year in energy costs.

This summer, instead of blasting the air conditioner (and blowing your electricity bills through the roof), you can take simple actions that will help you beat the heat. For example, replacing a dirty, clogged air filter with a clean one can lower your air conditioner’s energy consumption by 5-15 percent, while using a ceiling fan will allow you to raise the thermostat setting about 4 degrees without impacting your comfort.

Whether you’re looking to save on cooling costs with your current air conditioner or you want to upgrade to a more energy-efficient model, our new Energy Saver 101 infographic has you covered. From how air conditioners work to the different types of systems on the market to proper maintenance, the infographic lays out everything you need to know about home cooling. Plus, throughout the infographic you’ll find energy-saving tips and advice on common air conditioner problems.

With just a few small changes, you can relax in comfort this summer while saving some cold, hard cash.



Principles of Heating and Cooling

Understanding how heat is transferred from the outdoors into your home and from your home to your body is important for understanding the challenge of keeping your house cool. Understanding the processes that help keep your body cool is important in understanding cooling strategies for your home.

Principles of Heat Transfer

Heat is transferred to and from objects -- such as you and your home -- via three processes: conduction, radiation, and convection.

Conduction is heat traveling through a solid material. On hot days, heat is conducted into your home through the roof, walls, and windows. Heat-reflecting roofs, insulation, and energy efficient windows will help to reduce that heat conduction.

Radiation is heat traveling in the form of visible and non-visible light. Sunlight is an obvious source of heat for homes. In addition, low-wavelength, non-visible infrared radiation can carry heat directly from warm objects to cooler objects. Infrared radiation is why you can feel the heat of a hot burner element on a stovetop, even from across the room. Older windows will allow infrared radiation coming from warm objects outside to radiate into your home; shades can help to block this radiation. Newer windows have low-e coatings that block infrared radiation. Infrared radiation will also carry the heat of your walls and ceiling directly to your body.

Convection is another means for the heat from your walls and ceiling to reach you. Hot air naturally rises, carrying heat away from your walls and causing it to circulate throughout your home. As the hot air circulates past your skin (and you breathe it in), it warms you.

Cooling Your Body

Your body can cool down through three processes: convection, radiation, and perspiration. Ventilation enhances all these processes. You can also cool your body via conduction -- some car seats now feature cooling elements, for instance -- but this is not generally practical for use in your home.

Convection occurs when heat is carried away from your body via moving air. If the surrounding air is cooler than your skin, the air will absorb your heat and rise. As the warmed air rises around you, cooler air moves in to take its place and absorb more of your warmth. The faster this convecting air moves, the cooler you feel.

Radiation occurs when heat radiates across the space between you and the objects in your home. If objects are warmer than you are, heat will travel toward you. Removing heat through ventilation reduces the temperature of the ceiling, walls, and furnishings. The cooler your surroundings, the more you will radiate heat to the objects, rather than the other way around.

Perspiration can be uncomfortable, and many people would prefer to stay cool without it. However, during hot weather and physical exercise, perspiration is the body's powerful cooling mechanism. As moisture leaves your skin pores, it carries a lot of heat with it, cooling your body. If a breeze (ventilation) passes over your skin, that moisture will evaporate more quickly, and you'll be even cooler.



Central Air Conditioning

Central air conditioners circulate cool air through a system of supply and return ducts. Supply ducts and registers (i.e., openings in the walls, floors, or ceilings covered by grills) carry cooled air from the air conditioner to the home. This cooled air becomes warmer as it circulates through the home; then it flows back to the central air conditioner through return ducts and registers. To learn how central air conditioners compare to other cooling systems, check out our Energy Saver 101 Infographic: Home Cooling.

Air conditioners help to dehumidify the incoming air, but in extremely humid climates or in cases where the air conditioner is oversized, it may not achieve a low humidity. Running a dehumidifier in your air conditioned home will increase your energy use, both for the dehumidifier itself and because the air conditioner will require more energy to cool your house. A preferable alternative is a dehumidifying heat pipe, which can be added as a retrofit to most existing systems.

Types of Central Air Conditioners

A central air conditioner is either a split-system unit or a packaged unit.

In a split-system central air conditioner, an outdoor metal cabinet contains the condenser and compressor, and an indoor cabinet contains the evaporator. In many split-system air conditioners, this indoor cabinet also contains a furnace or the indoor part of a heat pump. The air conditioner's evaporator coil is installed in the cabinet or main supply duct of this furnace or heat pump. If your home already has a furnace but no air conditioner, a split-system is the most economical central air conditioner to install.

In a packaged central air conditioner, the evaporator, condenser, and compressor are all located in one cabinet, which usually is placed on a roof or on a concrete slab next to the house's foundation. This type of air conditioner also is used in small commercial buildings. Air supply and return ducts come from indoors through the home's exterior wall or roof to connect with the packaged air conditioner, which is usually located outdoors. Packaged air conditioners often include electric heating coils or a natural gas furnace. This combination of air conditioner and central heater eliminates the need for a separate furnace indoors.

Choosing or Upgrading Your Central Air Conditioner

Central air conditioners are more efficient than room air conditioners. In addition, they are out of the way, quiet, and convenient to operate. To save energy and money, you should try to buy an energy-efficient air conditioner and reduce your central air conditioner's energy use. In an average air-conditioned home, air conditioning consumes more than 2,000 kilowatt-hours of electricity per year, causing power plants to emit about 3,500 pounds of carbon dioxide and 31 pounds of sulfur dioxide.

If you are considering adding central air conditioning to your home, the deciding factor may be the need for ductwork.

If you have an older central air conditioner, you might choose to replace the outdoor compressor with a modern, high-efficiency unit. If you do so, consult a local heating and cooling contractor to assure that the new compressor is properly matched to the indoor unit. However, considering recent changes in refrigerants and air conditioning designs, it might be wiser to replace the entire system.

Today's best air conditioners use 30% to 50% less energy to produce the same amount of cooling as air conditioners made in the mid 1970s. Even if your air conditioner is only 10 years old, you may save 20% to 40% of your cooling energy costs by replacing it with a newer, more efficient model.

Proper sizing and installation are key elements in determining air conditioner efficiency. Too large a unit will not adequately remove humidity. Too small a unit will not be able to attain a comfortable temperature on the hottest days. Improper unit location, lack of insulation, and improper duct installation can greatly diminish efficiency.

When buying an air conditioner, look for a model with a high efficiency. Central air conditioners are rated according to their seasonal energy efficiency ratio (SEER). SEER indicates the relative amount of energy needed to provide a specific cooling output. Many older systems have SEER ratings of 6 or less. The minimum SEER allowed today is 13. Look for the ENERGY STAR® label for central air conditioners with SEER ratings of 13 or greater, but consider using air conditioning equipment with higher SEER ratings for greater savings.

New residential central air conditioner standards went into effect on January 23, 2006. Air conditioners manufactured after January 26, 2006 must achieve a SEER of 13 or higher. SEER 13 is 30% more efficient than the previous minimum SEER of 10. The standard applies only to appliances manufactured after January 23, 2006. Equipment with a rating less than SEER 13 manufactured before this date may still be sold and installed.

The average homeowner will remain unaffected by this standard change for some time to come. The standards do not require you to change your existing central air conditioning units, and replacement parts and services should still be available for your home's systems. The "lifespan" of a central air conditioner is about 15 to 20 years. Manufacturers typically continue to support existing equipment by making replacement parts available and honoring maintenance contracts after the new standard goes into effect.

Other features to look for when buying an air conditioner include:

  • A thermal expansion valve and a high-temperature rating (EER) greater than 11.6, for high-efficiency operation when the weather is at its hottest
  • A variable speed air handler for new ventilation systems
  • A unit that operates quietly
  • A fan-only switch, so you can use the unit for nighttime ventilation to substantially reduce air-conditioning costs
  • A filter check light to remind you to check the filter after a predetermined number of operating hours
  • An automatic-delay fan switch to turn off the fan a few minutes after the compressor turns off.

Installation and Location of Air Conditioners

If your air conditioner is installed correctly, or if major installation problems are found and fixed, it will perform efficiently for years with only minor routine maintenance. However, many air conditioners are not installed correctly. As an unfortunate result, modern energy-efficient air conditioners can perform almost as poorly as older inefficient models.

When installing a new central air conditioning system, be sure that your contractor:

  • Allows adequate indoor space for the installation, maintenance, and repair of the new system, and installs an access door in the furnace or duct to provide a way to clean the evaporator coil
  • Uses a duct-sizing methodology such as the Air Conditioning Contractors of America (ACCA) Manual D
  • Ensures there are enough supply registers to deliver cool air and enough return air registers to carry warm house air back to the air conditioner
  • Installs duct work within the conditioned space, not in the attic, wherever possible
  • Seals all ducts with duct mastic and heavily insulates attic ducts
  • Locates the condensing unit where its noise will not keep you or your neighbors awake at night, if possible
  • Locates the condensing unit where no nearby objects will block airflow to it
  • Verifies that the newly installed air conditioner has the exact refrigerant charge and airflow rate specified by the manufacturer
  • Locates the thermostat away from heat sources, such as windows or supply registers.

If you are replacing an older or failed split system, be sure that the evaporator coil is replaced with a new one that exactly matches the condenser coil in the new condensing unit. (The air conditioner's efficiency will likely not improve if the existing evaporator coil is left in place; in fact, the old coil could cause the new compressor to fail prematurely.)

What does this mean for me?

  • Central air conditioning systems are thermostatically controlled and convenient to use.
  • Central air conditioning systems must be installed properly to operate efficiently.
  • Central air conditioning systems can share ductwork with your heating system.



#AskEnergySaver: Home Cooling

To help you save money by saving energy, we launched #AskEnergySaver -- an online series that gives you access to some of the Energy Department’s home energy efficiency experts. During 2014, experts from the Department and our National Labs will be answering your energy-saving questions and sharing their advice on ways to improve your home’s comfort.

Summer’s sultry weather can take a toll on more than just your hair. For many households that rely on air conditioning to keep cool, summer’s heat and humidity can lead to higher energy bills. That’s why this month, we asked you to share your home cooling questions.

To answer them, we turned to Dr. Max Sherman, a senior scientist at the Energy Department’s Lawrence Berkeley National Lab. With more than 30 years of experience in building efficiency, Sherman’s research focuses on the connection between heating and cooling equipment, air leakage and indoor air quality.

What is the key to lowering cooling costs? Does a fan use more energy in certain circumstances?
-- from PurpleLivesOn via email

Max Sherman: A fan consumes very little energy compared to actual air conditioning. If running a fan provides the comfort you need, then it is going to be more economical.

If you need to use your cooling system, you can cut costs in several ways: 

  • Lower the cooling load: Reducing the amount of heat that gets in your house will keep your air conditioner from working as hard, and that means lower energy bills for you. A few ways to lower your home’s cooling load include shading your windows and roof, incorporating high-albedo (or white) surfaces, such as a cool roof, and increasing your home’s insulation. In humid climates, it is important to decrease excess air leakage. Also keep in mind that internal heat sources, such as your oven, can add to your cooling load.
  • Improve the efficiency of your equipment: At the simplest, improving the efficiency means keeping equipment in tune -- ensuring your system has proper airflow, is fully charged and has clean air filters. It also means reducing any duct leakage and insulating ducts if possible. For longer-term investments, consider replacing your air conditioner. New high efficiency cooling equipment uses substantially less energy to provide the same cooling services as old equipment.
  • Don’t cool more than you need: Why waste money cooling spaces you aren’t using? Instead, raise your thermostat when you are at work or shut off your air conditioner when on vacation. If you aren’t using some rooms, close the registers. You can also use ventilative cooling, such as whole-house cooling fans, economizers (a technology that pulls in outside air when it is cooler than the air in the house) and evaporative cooling, when conditions permit.

For more on air conditioners, explore ASHRAE’s top ten things about air conditioning.

What are other options for cooling your house without using air conditioning?
-- from Demola Livingthedreamplan Eff on Facebook

MS: There are a few techniques that are useful for staying cool without turning on your air conditioner:

  • When the outside conditions are cooler than inside, open your house up to mechanical ventilation -- such as whole-house fans -- or natural ventilation. This will remove the heat generated inside your house.
  • Keep your house cool by reducing the sources of heat. These can either be internal, such as the appliances in your kitchen, or external, such as sunlight.
  • Air motion of any kind makes the body feel cooler -- at least until the air gets above body temperature. A ceiling or portable fan can make you feel cooler by creating a wind chill.
  • If there are big day-night temperature differences, ventilate by opening windows at night to pre-cool the house and minimize temperature rise during the day.

We have a forced air system that is used for cooling and heating. Is it less costly to close the door of a room that is used very little? Or is it generally more beneficial to leave that door open so the air is circulated to the rest of the house?
-- from Darneson12 via email

MS: If there is a room in your house that you don’t use, you’ll save costs by isolating it from the rest of the house. To do so, you could shut the door and also shut the supply register to that room. But don’t do this to too many rooms at once because it could cause problems for your central system. If too many registers are blocked off, the pressure in the duct system will build up and reduce the airflow in the system. Not only can this result in new duct leakage and lower efficiency, it could also cause the system’s cooling coils to freeze up.



Tips: Programmable Thermostats

You can save as much as 10% a year on heating and cooling by simply turning your thermostat back 7°-10°F for 8 hours a day from its normal setting. (If you have a heat pump, don't do this without a programmable thermostat). You can do this automatically by using a programmable thermostat and scheduling the times you turn on the heating or air conditioning. As a result, the equipment doesn't operate as much when you are asleep or not at home.

Programmable thermostats can store multiple daily settings (six or more temperature settings a day) that you can manually override without affecting the rest of the daily or weekly program.



Built to Last: York LX Series Packaged Units

At York, creating quality home comfort products is our central commitment to every customer. This focus led to creating a completely new packaged unit design that delivers outstanding performance and reliability. Our team of engineering and manufacturing experts used a unique quality process.



Evaporative Coolers

In low-humidity areas, evaporating water into the air provides a natural and energy-efficient means of cooling. Evaporative coolers, also called swamp coolers, rely on this principle, cooling outdoor air by passing it over water-saturated pads, causing the water to evaporate into it. The 15°- to 40°F-cooler air is then directed into the home, and pushes warmer air out through windows.

When operating an evaporative cooler, windows are opened part way to allow warm indoor air to escape as it is replaced by cooled air. Unlike central air conditioning systems that recirculate the same air, evaporative coolers provide a steady stream of fresh air into the house.

Evaporative coolers cost about one-half as much to install as central air conditioners and use about one-quarter as much energy. However, they require more frequent maintenance than refrigerated air conditioners and they're suitable only for areas with low humidity.

Sizing and Selection

Evaporative coolers are rated by the cubic feet per minute (cfm) of air that they deliver to the house. Most models range from 3,000 to 25,000 cfm. Manufacturers recommend providing enough air-moving capacity for 20 to 40 air changes per hour, depending on climate.


Evaporative coolers are installed in one of two ways: the cooler blows air into a central location, or the cooler connects to ductwork, which distributes the air to different rooms. Central-location installations work well for compact houses that are open from room to room. Ducted systems are required for larger houses with hallways and multiple bedrooms.

Most people install down-flow evaporative coolers on the roofs of their houses. However, many experts prefer to install ground-mounted horizontal units, which feature easier maintenance and less risk of roof leaks.

Small horizontal-flow coolers are installed in windows to cool a room or section of a home. These portable evaporative coolers work well in moderate climates, but may not be able to cool a room adequately in hot climates. Room evaporative coolers are becoming more popular in areas of the western United States with milder summer weather. They can reduce the temperature in a single room by 5° to 15°F.

Small, portable evaporative coolers on wheels are now available as well. Although the units have the advantage of portability, their cooling ability is limited by the humidity within your home. Generally, these units will provide only a slight cooling effect.


An evaporative cooler should have at least two speeds and a vent-only option. During vent-only operation, the water pump does not operate and the outdoor air is not humidified. This lets you use the evaporative cooler as a whole-house fan during mild weather.

Control the cooler's air movement through the house by adjusting window openings. Open the windows or vents on the leeward side of the house to provide 1 to 2 square feet of opening for each 1,000 cfm of cooling capacity. Experiment to find the right windows to open and the correct amount to open them. If the windows are open too far, hot air will enter. If the windows are not open far enough, humidity will build up in the home.

You can regulate both temperature and humidity by opening windows in the areas you want to cool, and closing windows in unoccupied areas. Where open windows create a security issue, install up-ducts in the ceiling. Up-ducts open to exhaust warm air into the attic as cooler air comes in from the evaporative cooler. Evaporative coolers installed with up-ducts will need additional attic ventilation.

Optional filters remove most of the dust from incoming air -- an attractive option for homeowners concerned about allergies. Filters can also reduce the tendency of some coolers to pull water droplets from the pads into the blades of the fan. Most evaporative coolers do not have air filters as original equipment, but they can be fitted to the cooler during or after installation.

Evaporative Cooler Maintenance

Save yourself a lot of work and money by draining and cleaning your evaporative cooler regularly. Build-up of sediment and minerals should be regularly removed. Coolers need a major cleaning every season, and may need routine maintenance several times during the cooling season.

The more a cooler runs, the more maintenance it will need. In hot climates where the cooler operates much of the time, look at the pads, filters, reservoir, and pump at least once a month. Replace the pads at least twice during the cooling season, or as often as once a month during continuous operation.

Some paper and synthetic cooler pads can be cleaned with soap and water or a weak acid according to manufacturer's instructions. Filters should be cleaned when the pads are changed or cleaned. Be sure to disconnect the electricity to the unit before servicing it.

Two-Stage Evaporative Coolers

Two-stage evaporative coolers are newer and even more efficient. They use a pre-cooler, more effective pads, and more efficient motors, and don't add as much humidity to the home as single-stage evaporative coolers. Because of their added expense, they are most often used in areas where daytime temperatures frequently exceed 100°F.

Drawbacks of Evaporative Coolers

Evaporative coolers should not be used in humid climates because they add humidity to the air in your home. Also, they cool your house down to a higher temperature than an air conditioner would, and they require simple maintenance about once a month. If the cooler is installed on the roof, there is some roof deterioration caused by routine maintenance trips. A sunlit rooftop cooler will be about 1°F less effective than a shaded cooler. Rooftop maintenance also requires using a ladder, which may be an inconvenience.

By their nature, evaporative coolers also continually use water. In areas with limited water supplies, homeowners may be concerned about the water-use impact of adding an evaporative cooler.

What does this mean for me?

  • If you live in a warm, dry climate, you can save money on utility bills and stay comfortable during the cooling season by installing an evaporative cooler.
  • Evaporative coolers add humidity to indoor air, a benefit in dry, warm climates.
  • Unlike air conditioners that recirculate air, an evaporative cooler adds fresh air to your home.



Room Air Conditioners

Room or window air conditioners cool rooms rather than the entire home or business. If they provide cooling only where they're needed, room air conditioners are less expensive to operate than central units, even though their efficiency is generally lower than that of central air conditioners. For ways to save on cooling costs with a room air conditioner, check out our Energy Saver 101 Infographic: Home Cooling.

Smaller room air conditioners (i.e., those drawing less than 7.5 amps of electricity) can be plugged into any 15- or 20-amp, 115-volt household circuit that is not shared with any other major appliances. Larger room air conditioners (i.e., those drawing more than 7.5 amps) need their own dedicated 115-volt circuit. The largest models require a dedicated 230-volt circuit.

Energy Efficiency of Room Air Conditioners

A room air conditioner's efficiency is measured by the energy efficiency ratio (EER). The EER is the ratio of the cooling capacity (in British thermal units [Btu] per hour) to the power input (in watts). The higher the EER rating, the more efficient the air conditioner. National appliance standards require room air conditioners to have an energy efficiency ratio (EER) ranging from 8.0–9.8 or greater, depending on the type and capacity, and ENERGY STAR® qualified room air conditioners have even higher EER ratings.

The Association of Home Appliance Manufacturers reports that the average EER of room air conditioners rose 47% from 1972 to 1991. If you own a 1970s-vintage room air conditioner with an EER of 5 and you replace it with a new one with an EER of 10, you will cut your air conditioning energy costs in half.

When buying a new room air conditioner, look for units with an EER of 10.0 or above. Check the EnergyGuide label for the unit, and also look for room air conditioners with the ENERGY STAR label.

Sizing and Selecting a Room Air Conditioner

The required cooling capacity for a room air conditioner depends on the size of the room being cooled -- room air conditioners generally have cooling capacities that range from 5,500 Btu per hour to 14,000 Btu per hour. A common rating term for air conditioning size is the "ton," which is 12,000 Btu per hour.

Proper sizing is very important for efficient air conditioning. A bigger unit is not necessarily better because a unit that is too large will not cool an area uniformly. The oversized unit will also cool the room to its thermostat set point and shut down prior to properly dehumidifying the room, leaving the area feeling damp or "clammy." A small unit running for an extended period operates more efficiently and is more effective at dehumidifying than a large unit that cycles on and off too frequently.

Based on size alone, an air conditioner generally needs 20 Btu for each square foot of living space. Other important factors to consider when selecting an air conditioner are room height, local climate, shading, and window size.

Verify that your home's electrical system can meet the unit's power requirements. Room units operate on 115-volt or 230-volt circuits. The standard household receptacle is a connection for a 115-volt branch circuit. Large room units rated at 115 volts may require a dedicated circuit and room units rated at 230 volts may require a special circuit.

If you are mounting your air conditioner near the corner of a room, look for a unit that can direct its airflow in the desired direction for your room layout. If you need to mount the air conditioner at the narrow end of a long room, then look for a fan control known as "Power Thrust" or "Super Thrust" that sends the cooled air farther into the room.

Other features to look for include:

  • A filter that slides out easily for regular cleaning
  • Logically arranged controls
  • A digital readout for the thermostat setting
  • A built-in timer.

Installing and Operating Your Room Air Conditioner

A little planning before installing your air conditioner will save you energy and money. The unit should be level when installed, so that the inside drainage system and other mechanisms operate efficiently.

Don't place lamps or televisions near your air-conditioner's thermostat. The thermostat senses heat from these appliances, which can cause the air conditioner to run longer than necessary.

Set your air conditioner's thermostat as high as is comfortably possible in the summer. The less difference between the indoor and outdoor temperatures, the lower your overall cooling bill will be. Don't set your thermostat at a colder setting than normal when you turn on your air conditioner; it will not cool your home any faster and could result in excessive cooling and unnecessary expense.

Set the fan speed on high, except on very humid days. When humidity is high, set the fan speed on low for more comfort. The low speed on humid days will cool your home more effectively and remove more moisture from the air because of slower air movement through the cooling equipment.

Consider using an interior fan in conjunction with your window air conditioner to spread the cooled air through your home without greatly increasing electricity use.

Remember that efficient operation of any air conditioning system relies on a properly insulated and air sealed home. For more information, see Home Energy Audits and Detecting Air Leaks.



Ductless Mini-Split Air Conditioners

Ductless, mini split-system air-conditioners (mini splits) have numerous potential applications in residential, commercial, and institutional buildings. The most common applications are in multifamily housing or as retrofit add-ons to houses with "non-ducted" heating systems, such as hydronic (hot water heat), radiant panels, and space heaters (wood, kerosene, propane). They can also be a good choice for room additions and small apartments, where extending or installing distribution ductwork (for a central air-conditioner or heating systems) is not feasible. Check out our Energy Saver 101 infographic on home cooling to learn how ductless, mini-split air conditioners stack up against other cooling systems.

Like central systems, mini splits have two main components: an outdoor compressor/condenser, and an indoor air-handling unit. A conduit, which houses the power cable, refrigerant tubing, suction tubing, and a condensate drain, links the outdoor and indoor units.


The main advantages of mini splits are their small size and flexibility for zoning or heating and cooling individual rooms. Many models can have as many as four indoor air handling units (for four zones or rooms) connected to one outdoor unit. The number depends on how much heating or cooling is required for the building or each zone (which in turn is affected by how well the building is insulated). Each of the zones will have its own thermostat, so you only need to condition that space when it is occupied, saving energy and money.

Ductless mini split systems are also often easier to install than other types of space conditioning systems. For example, the hook-up between the outdoor and indoor units generally requires only a three-inch (~8 centimeter [cm]) hole through a wall for the conduit. Also, most manufacturers of this type of system can provide a variety of lengths of connecting conduits. So, if necessary, you can locate the outdoor unit as far away as 50 feet (~15 meters [m]) from the indoor evaporator. This makes it possible to cool rooms on the front side of a building house with the compressor in a more advantageous or inconspicuous place on the outside of the building.

Since mini splits have no ducts, they avoid the energy losses associated with ductwork of central forced air systems. Duct losses can account for more than 30% of energy consumption for space conditioning, especially if the ducts are in an unconditioned space such as an attic.

Compared with other add-on systems, mini splits offer more flexibility in interior design options. The indoor air handlers can be suspended from a ceiling, mounted flush into a drop ceiling, or hung on a wall. Floor-standing models are also available. Most indoor units have profiles of about seven inches (~18 cm) deep and usually come with sleek, high-tech-looking jackets. Many also offer a remote control to make it easier to turn the system on and off when it's positioned high on a wall or suspended from a ceiling. Split-systems can also help to keep your home safer, because there is only a small hole in the wall. Through-the-wall and window mounted room air-conditioners can provide an easy entrance for intruders.


The primary disadvantage of mini splits is their cost. Such systems cost about $1,500 to $2,000 per ton (12,000 Btu per hour) of cooling capacity. This is about 30% more than central systems (not including ductwork) and may cost twice as much as window units of similar capacity.

The installer must also correctly size each indoor unit and judge the best location for its installation. Oversized or incorrectly located air-handlers often result in short-cycling, which wastes energy and does not provide proper temperature or humidity control. Too large a system is also more expensive to buy and operate.

Some people may not like the appearance of the indoor part of the system. While less obtrusive than a window room air conditioner, they seldom have the built-in look of a central system. There must also be a place to drain condensate water near the outdoor unit.

Qualified installers and service people for mini splits may not be easy to find. In addition, most conventional heating and cooling contractors have large investments in tools and training for sheet metal duct systems. They need to use (and charge for) these to earn a return on their investment, so they may not recommend ductless systems except where a ducted system would be difficult for them to install.

What does this mean for me?

  • A ductless mini-split air conditioner is easier to install than a central air conditioning system.
  • A ductless mini-split air conditioner provides zoned air conditioning without ducting.
  • A ductless mini-split air conditioner is relatively easy to install and does not provide an entry point for intruders as some room air conditioners do.