Air Conditioner Buying Guide

Air Conditioner Buying Guide

The Basics: Air Conditioners

Room air conditioner is an enclosed cooling unit that can be mounted in a window, through a wall or in a portable cabinet on a floor near a window. Its job is to cool the air in a small, confined area as directed by the unit's controls. Some room air conditioners have other functions as well. For example, reverse intake air conditioners also work as heaters, making them a home appliance that is useful nearly year-round.

Room air conditioners work similarly to central air conditioning systems, but are contained in one compact unit. When the room air conditioner unit is on, the condenser pulls in the refrigerant gas and pressurizes it, raising the temperature of the gas. The heated high-pressure gas then travels to the condenser coils on the outdoor side of the unit where fins distribute the collected heat. The cooled gas then condenses into a liquid that moves indoor to the evaporator coils where it absorbs heat from the room. A fan moves the air through the unit and expels the cooled air into the room.

A thermostat controls the unit's operation. Many units now have advanced electronic controls that can adjust one degree at a time, rather than the primitive "cool" or "cooler" dial settings that were once common. The electronic controls also may regulate the fan speed, operation mode, timer and other settings. In addition, many air conditioners at a variety of price points now include a remote.

An air conditioner unit's cooling power is measured in British Thermal Units or Btu per hour. One Btu can raise or lower the temperature of 1 pound of water 1 degree Fahrenheit. All room air conditioners are rated by the maximum Btu/hr. Keep in mind that even the smallest room air conditioners may have thousands of Btu per hour. To keep these numbers is the proper perspective, remember to compare the Btu between systems. Generally, the more Btu, the larger an area the air conditioner can cool.

Small air conditioners are rated for energy efficiency by EnergyStar.gov, a service of the U.S. Department of Energy and the Environmental Protection Agency. The Energy Efficiency Rating (EER) is the cooling capacity in Btu divided by the watts of electrical power the unit uses. To earn the Energy Star compliant rating, a unit must have an EER 10 percent higher than conventional models.

What do these ratings really mean to you? The Department of Energy calculates that replacing a 10-year-old room air conditioner with a similar but new Energy Star qualified model saves an average of $25 a year on the typical electric bill.

Another important factor is quietness. A window air conditioner in a bedroom, for example, should be extremely quiet so that it does not interfere with sleep cycles. The quieter air conditioners are well insulated to minimize rattling when the fan is running. A window air conditioner that has little support -- or that is not installed correctly -- also can rattle within a window frame.

All of the room air conditioners reviewed here are designed to operate in 115-volt (110-120V) branch circuits as found in most homes in the United States. Larger units may require 230-volt service and a dedicated circuit.

Warranties vary on room air conditioners. Many manufacturers offer a 1-year full warranty, while some offer a 5-year warrant to cover the air conditioner's sealed system or major components such as the condenser, evaporator, fan and controls. Many have a 5-year limited warranty on the condenser (no moving parts) and 1-year warranty on everything else. A few models have in-home warranties, which means the manufacturer will send a service person to your home if there are problems with your air conditioner, but these warranties are not common.

Here are five key questions to answer before you purchase an air conditioner:

How big is the area you want to cool? Room air conditioners are rated in Btu capacity. For a small room (100 to 300 square feet), select an air conditioner of 5,000 to 6,000 Btu/hr. For a medium-size room (300 to 600 square feet) choose a unit of 8,000 to 9,000 Btu/hr. For larger rooms (600 to 1,000 square feet) the best choice is an air conditioner of 10,000 to 15,000 Btu/hr. These are guidelines. If the insulation in your home is minimal or the air conditioner sits in a hot south-facing window, opt for a unit with higher Btu. Also remember that these calculations are for standard room heights; if the room you are cooling has a taller ceiling, you'll need about 10 percent more Btu to adequately cool the air in the room. If possible, avoid installing the cooling unit in a south-facing window that gets lots of sunlight as it reduces the unit's efficiency. Keep in mind that if you buy an air conditioner with a higher Btu rating than you really need, it will cycle on and off too quickly. This means it will use more energy, cost more to operate and remove less humidity from the air. Alternatively, if you use an air conditioner with a low Btu to cool a too-large room, it will run continuously and cost more to operate.

Where is the best place to install an air conditioner? Many room air conditioners are installed seasonally in a window. Most residential windows open from the bottom and the majority of room air conditioners are designed to be placed on the sill with accordion-like extension panels that seal the opening and help prevent air loss. Some models are built for installation in side-sliding windows with an extension panel above the unit. Alternately, air conditioners can be installed more permanently through the wall to make a better seal and offer firmer support than a window. Another option is a portable air conditioner, which are enclosed in a rolling cabinet. Some vent the heat through a duct that can be placed in a nearby window; other portables use water from the dehumidifying process to cool the air.

Can an air conditioner do more than just cool a room? Yes, some also act as dehumidifiers and some do double-duty as heaters. Depending on where you live, humidity may be a problem or a necessity. For arid summer climates, an air conditioner with a built-in humidifier can add moisture to the air to make the room more comfortable. For other areas, hot days are exacerbated by humidity. An air conditioner with built-in dehumidifier can remove moisture from the air. Some models can also serve as heaters to warm the air as needed. This means that they can stay in place year-round and serve multiple purposes.

How important are controls? Older room air conditioners were controlled by a single dial that was set based on an estimate of the result: Set it most of the way to the left, for example, to keep the room at about 72 degrees Fahrenheit. Today's air conditioners are much smarter; you can set a unit for 72 degrees and it will maintain the air temperature within 1 degree of that point. For convenience, many room air conditioners now have wireless remote controls that let you change settings -- even the direction of the airflow -- from across the room. Many units have timers to program the unit to start or shut off, so you can set the AC to turn on just before you get home or turn off when you go to sleep. An important feature of most room air conditioners is the filtration system. Nearly all units have a cleanable foam filter. Some use electronic air filtration to remove dust and pollens from the air. Make sure that the filtration system is adequate and easy to maintain. It's important to check that extra features, such as a heater or dehumidifier, have adequate and easy-to-use controls. Also, be sure that there is an electrical unit near where you will use the unit. Most models run on standard three-prong 115-volt plugs.

What is your cooling budget? How much can you invest in cooling a room? If the selected room only gets hot during a couple of weeks in the summer, you probably want to invest in a less expensive model. If the cooling season is long and the room is frequently populated, you should invest in a more expensive and more powerful unit. Here are some guidelines: Room air conditioners range from $100 to $1,500 with most of them in the range of $250-$600. Lower priced models often have manual controls and higher priced units may include a dehumidifier or a heater. For about $350, you'll get an energy-efficient 8,000 to 10,000 Btu air conditioner with adequate features and a remote control, which is just right for many applications.

How to Shop

Room air conditioners are typically a do-it-yourself project. You will buy it in a box, unpack it and install it yourself. The model you select can be "shopped" among numerous retailers, searching for the best price and after-sale service. Big-box stores -- such as The Home Depot, Lowes, Sears and Wal-Mart -- sell most of the room air conditioners on the market, though regional hardware stores can sometimes beat their prices on selected models, as can an increasing number of online retailers. In many cases, a model you find at Lowe's won't be available at The Home Depot -- but a similar model will.

At what time of the year you shop also is important. The selling season for air conditioners varies across the United States and Canada, stretching from May to September. Most units are sold in July and August. Shopping for an air conditioner early or late in your local summer season means you can find reduced prices on units by as much as 25 percent. An excessively hot local summer can quickly drain the stores of units that won't be reordered until next year, while a cooler-than-normal summer can leave many units on the shelves that retailers need to sell on clearance, so make sure to plan ahead in order to pay less.

Room air conditioners are comforting low-maintenance home appliances that can serve the cooling needs of a room for many years at a relatively low price. When it comes to room air conditioners, knowing what, when and how to buy can take the heat off.