The Basics: Air Conditioners
A room air conditioner is an enclosed cooling unit that can be mounted in a window, through a wall, or in a portable case on the 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.
A room air conditioner doesn't really cool a room. It removes the heat from the air and takes it elsewhere. Pressurized R-22 refrigerant flows through the room air conditioner. When the 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. The thermostat controls the unit's operation. Some air conditioners have mechanical controls (knobs and pushbuttons) while most others have electronic touchpads that regulate the mode, temperature setpoint, timer and other conveniences.
How much cooling a unit can do is measured in British thermal units or Btu per hour. One Btu can raise or lower the temperature of one pound of water 1 degree Fahrenheit. All room air conditioners are rated by maximum Btu/hr.
To help consumers choose a unit, small air conditioners are rated for energy efficiency by EnergyStar.gov, a service of the U.S. Dept. 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 of 10 percent higher than conventional models.
What do these ratings really mean to you? The Dept. 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 the master bedroom, for example, should be extremely quiet to allow sleeping. The quieter air conditioners have solid frames with cushioning to minimize rattle when the fan is running. A window air conditioner that has little support below it also can rattle within the 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 from 1 to 5 years and cover the major components: 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 mean they will send a service person to your home if there are problems with your air conditioner.
Five Key Questions You Need Answered Before You Buy
1. How big is the area you want to cool? Room air conditioners are rated in Btu capacity. For a small room (100-300 square feet), select an air conditioner of 5,000-6,000 Btu/hr. For a medium-size room (300-600 square feet) choose a unit of 8,000-9,000 Btu/hr. For larger rooms (600-1,000 square feet) the best choice is an air conditioner of 10,000-15,000 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 more Btu to adequately cool the air in the room. Also, if possible, avoid installing the cooling unit in a south-facing window that gets lots of sunlight as it reduces the unit's efficiency.
2. Where is the best place to install your 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 wing panels that seal the opening from air loss. Some models are built for installation in side-sliding windows with the wing panel above the unit. Alternately, air conditioners can be installed more permanently through the wall to make a better seal and offer better support than in a window. Another option is portable air conditioners designed to stand on the floor. Some vent the heat out through a duct that can be placed in a nearby window; other portables use water from the dehumidifying process to cool the air.
3. Can an air conditioner do more than just cool a room? Some room air conditioners can do more than just cool the air. 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, such as the Midwest, 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 (actually heat pumps) to seasonally warm the air as needed. This means that they can stay in place year-round and serve multiple purposes.
4. 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 setpoint. For convenience, many room air conditioners now have wireless remote controls that let you change settings -- even the direction of the air flow -- from across the room. Many units have timers that can be programmed when 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 on the one you buy is adequate and easy to maintain. And make sure 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 nearby where you will install the unit. Most models run on standard three-prong 115-volt plugs.
5. 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 $600 with most of them in the mid-range of $250-$450. Lower priced models often have mechanical controls (knobs) and higher priced units include a dehumidifier and maybe even a heater. For about $350, you'll get an energy-efficient 8-10,000 Btu air conditioner with adequate features and a remote control, which is just right for many applications.
How to Shop
Room air conditioners are a commodity. 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 WalMart -- sell most of the room air conditioners on the market, though regional hardware stores can sometimes beat their prices on selected models. In many cases, a model you find at Lowe's won't be available at The Home Depot -- but a similar model will. Room ACs are also sold online by major retailers.
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. Knowing what, when and how to buy a room air conditioner can take the heat off.
