Although a central air conditioning system may be best for some households, they do come with a high price tag and require expert installation. They also cost more to operate than a smaller room air conditioner. For this reason, when only a certain room or area of the home requires cooling, a room air conditioner may be the best choice. But there are several models suitable for cooling a single room or area as well as other considerations, so this purchase should not be made in haste.

Types of Room Air Conditioners

The type of room air conditioner you need depends partially on how much installation you're prepared to do and where you want it. This may be an easy decision if you own your home but for a tenant,it may require a landlord's approval.

Air Conditioner Types:

• Window-mounted unit - most popular and economical

• Wall-mounted unit - requires some renovation work

• Window/wall units allow either installation.

• Portable air conditioners - mobile units that exhaust hot air through a connection out a window.

• Split ductless or mini air systems are more expensive than window/wall units, but are less intrusive than a full central unit.

Deciding on Capacity to Cool a Certain Coverage Area

Manufacturers usually provide recommended coverage for a given model and buying a unit that's adequate to cool that area is very important. Under-sizing may be inadequate and oversizing for the room, you'll be paying for a benefit you may not need or use. Measure the area before you shop. These are the recommended BTU's for a given cooling area from Consumer Reports:

• Small room: 5,000 - 6,000 BTU for 100-300 sq. ft.

• Medium room: 7,000 - 8,200 BTU for 250-550 sq. ft.

• Large room: 9,800 to 12,500 BTU's for 350-950 sq. ft. area.

Energy Efficiency to Save in Electricity Costs

An EnergyStar® qualified air conditioner will save you about 30% less in energy costs over non-qualifying units. You should also consider the EER rating. Air conditioners that have been certified by the Association of Home Appliance Manufacturers (AHAM) carry an energy efficiency rating (EER). The higher the number, the less in operating costs. Therefore an air conditioner with an EER rating of 11 will cost less to operate than one with a rating of 6. Combine a high EER rating with EnergyStar and your new air conditioner will be most efficient. You may also want to take note of a CEE tier rating.

Benefits of Portable Air Conditioners

While a window or wall air conditioner is either permanently or seasonally installed for cooling a specific room, a portable unit is versatile and can be relocated in minutes to another room that needs cooling. While some mobile models are multifunction and can include dehumidifying, air purification or heating functions, others are simply cooling units. Though convenient, portable air conditioners are more expensive than window models and some can be very heavy to relocate, even though they have wheels. However, for some homes these units can be the perfect choice.

How Ductless Split Systems Work

Though often more efficient than wall or window units, ductless split systems do cost more and should be installed by a trained professional. They are however easier and quicker to install than a central system and since they cool only certain areas, operating costs will be lower. These systems involve a condenser that is placed outside the home, with one or more room units that are connected to the condenser, by through-the-wall refrigerant and electrical lines. Also called mini central or mini-split systems, they're a cheaper alternative with cooling benefits just where you need them.

Best Air Conditioner Features

• Electronic controls make the unit easy to set

• Remote control adds convenience especially at night

• Sleep or Energy Saver modes keep the room comfortable while saving energy costs

• Auto-restart is a must for brown out periods. Power outages are hard on compressors, but with this feature the unit will restart after a power failure without harming the unit.

• EnergyStar compliant and a high EER will save in energy costs.

• Programmable or delay start settings are ideal for having the room cooled just before you return home.

• Filter type, source and whether reusable

• Easy install kit

• Adjustable multi-way directional control

Installation Considerations for Window/Wall Units

Always measure the window area before shopping for an air conditioner. Consider the impact of losing a portion of the viewing area, as well as how you'll fill the rest of the window panel after inserting the air conditioner. Some use wood to block the rest of the pane, but a plastic panel may suffice and look better. When installing a wall unit, the installation may include a certain amount of building supplies and care should be taken to reduce hazards and avoid cutting into electrical or other wires. Window or wall units also need sufficient bracing and you may need an off-season cover.