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HVAC systems comparison: cooling
By Peter Boysen
Lets fix this
87% of U.S. homes are now equipped with air conditioning. If you are seeking to join that percentage or are considering changes to your current system, check out our comparison of central air conditioners, evaporative coolers and window units.
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Evaporative cooler |
Central air conditioner |
Window air conditioner |
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What it is |
Evaporative cooling systems, also called swamp coolers, use the simple process of air moving across a damp surface to cool an area. They are efficient and environmentally friendly, but they don't work well in high humidity. |
A central air conditioner combines the power of an outdoor condenser with an indoor evaporator to pull warm air from the interior of the home and move it outdoors. The cool air is then distributed throughout the home via ductwork. |
A window air conditioner, which can also be placed in a wall if preferred, provides cooling without the need for ductwork, a huge advantage in homes with none. They are generally unitary, meaning all the parts needed to provide the cooling power are contained within the single unit. |
Energy costs |
 An evaporative cooling system, or swamp cooler, can use 25-80% less energy than an air conditioning system or stand-alone unit. |
 A buildingwide or even housewide system can be the least affordable option when it comes to energy bills, as they often rely on one thermostat to cool a 2-story dwelling. Careful use and systems with multiple zones of coverage can increase efficiency, but using a single system to cool an entire building is still inefficient, which results in higher costs. Note: Newer systems are much more efficient that older models. If you are replacing a central air system that is more than 12 years old with an Energy Star model, expect to save about 30% on your cooling costs, according to the Environmental Protection Agency (EPA). |
These systems tend to cool only one room or perhaps a suite of rooms. As a result, their per-unit costs are lower, but more units would be needed to provide the same cooling power as a central air conditioning system. Still, if they are used to provide cooling only where needed, window air conditioners are less expensive to run than central units. |
Cooling power |
Cooling power varies depending on the ambient humidity of your environment. In arid places such as the American Southwest, a swamp cooler can provide relief. In the swamps of Florida or the bayous of Louisiana, though, the air is often so saturated with moisture that adding cool humidity won’t cool the air. |
A central air conditioner has the most power of any of these systems and brings the most energy to solving your heat problem. |
A smaller unit has less power, and turning up the cooling output comes at a cost—a noisier unit. When considering if a window unit makes sense for your home, consider which areas you want cooled and compare how many window units you would need to provide the same cooling coverage as a central air conditioner. Note: Don't buy a larger unit than you need thinking it will provide more cooling. An oversized unit actually cools less effectively and wastes money. Figure out the best size for your space on the EPA's room air conditioner page. |
Climate control |
Evaporative cooling does have at least two speeds and a vent-only option, but it focuses on increasing humidity, and so temperature control is going to be imprecise. |
Central air conditioning provides very precise control of the temperature and humidity. You may set your climate preferences using the system's thermostat and then leave it to do its cooling work. Keeping comfortably cool happens more automatically. Note: You cannot adjust climate per room. People have differing tolerances for temperature, and it may be difficult to please everybody. |
You do not have the ability to set precise temperature settings or address humidity with these units. The settings are manual and require your attention for every adjustment, but window units do allow for greater flexibility to create different climates per room. |
Energy efficiency |
Because evaporative coolers bring air from the outside directly into the living space, leaks aren’t an issue. |
As long as all of the ductwork is sealed and insulated properly, you should be able to maximize your energy efficiency, at least given the cost of operating such a large unit. It just takes one leak, however, to pull that chilled air away from where it is needed and keep the whole system running unnecessarily. Try these additional methods of lowering energy consumption: |
If you don't want to cool a particular space, you can just turn off that dedicated unit. This gives you flexibility, as you can turn each room, potentially, into its own climate control zone. |
Reliability |
Evaporative coolers have fewer internal parts than window and central air conditioners. The only two mechanical parts in most are the fan motor and the water pump. You therefore have fewer parts that can break, making repairs less frequent. Repairs for both parts also come at relatively low cost. |
As with any extensive system comprised of many parts, breakdowns are possible, especially as the unit ages. But you can depend the most on this sophisticated system to keep you comfortable. This is especially true if you tune up your system each year to ensure maximum output and efficiency. See our guide to air conditioner maintenance. |
Over time and with use, any unit will wear out. Check with your local home repair retailer to find the unit with the best reputation—and the best warranty. |
Lifespan |
Evaporative coolers can continue to cool you for about 15-20 years. |
The lifespan of a central air conditioner system is about 15-20 years. |
A quality window unit can last up to 10 years or beyond. Regular and careful cleaning can extend its life. Don't forget to cover the inside and outside of the unit during the winter months. |
Environmental effect |
Air conditioners and heat pumps rely on a refrigerant such as Freon to cool the air that’s circulating through the system. If a leak develops, the refrigerant can cause environmental damage. Swamp coolers, on the other hand, rely only on moisture to cool the dry air. It is the greenest option. |
As long as the refrigerant stays in the closed system, you shouldn't have any toxins entering the environment. |
Window units use refrigerant, too. If the unit stays leak-free, your yard and environment will stay toxin-free. They also don't use as much energy, so if you’re looking to control costs as well as the use of fossil fuel, selectively using these to cool can be a green option. |
Climate compatibility |
These work the best in arid climates, such as in the American Southwest and California. Unfortunately, in other parts of the country, the hottest months (July and August) tend to also be the wettest and most humid. Note: Using a swamp cooler in humid climates can accelerate corrosion and increase condensation, ruining your electronics, books and other moisture-sensitive products. |
These systems work in any climate. However, they might be more worth the expenditure in climates that are warm 8 or 9 months of the year. Note: Air conditioners tend to dry out the air, so dry skin and dehydration are possible if the climate is already arid. |
These units will work in any climate, but they might make more sense in a moderate part of the country, as in the American Northwest and the East Coast, as you are not as likely to need air conditioning for as much of the year. |
Affordability |
To operate one for your whole house, professionals recommend a two-stage system. The first stage cools the air from the outside, and then the second stage sends it to your ductwork. Average estimates for a 2,500-square-foot home run about $5,000 for the system—with existing ductwork. Plan to add another $3,000-$4,000 if your home does not have ductwork. |
If you have a home that is 2,500 square feet, plan on spending $3,000-$4,000 for your system. This cost only applies to homes with ductwork in place. If you need ductwork added, plan on adding about $4,000 to your total. |
The cost of each unit will depend on the cooling power that you need. Individual window units generally range from $150 to $500, based on the power provided. This means that it will be much cheaper to cool one space, but the cost of the units will add up if you have a larger house. |
To learn more about climate control, past and present, and the types of systems available to you today, read "What is HVAC?"
Peter Boysen
Peter has been teaching since 1996 and writing professionally since 2003. Specializing in writing on education and home repair, he has written for ON Magazine, Prestwick House and Bright Hub, among others. He has also completed 15 marathons, thanks to the patience of his wife and 4 children, and is feverishly finishing his first novel.