How Much Does an Air Conditioner Cost?

If the thought of facing the hot weather without air conditioning makes you break out in a sweat, you should know that you do have options that can bring you relief. Air conditioning can be delivered by a number of different products, from small window units to large central appliances with ductwork that can cool the entire house. But they all work in much the same way.

Warm air from the room, or house, gives up its heat to a refrigerant that runs through an evaporator coil. The cooled down air is blown back into the room while the refrigerant flows to a compressor that, as the name implies, compresses the refrigerant, making it hotter and denser. This then goes to a condenser where the heat in the refrigerant is released to the outside. Then the process repeats.

• ​For rooms up to 300 square feet: $200 to $500​
• ​For larger areas: $350 to $900​

An air conditioner's capacity is measured in BTUs (British Thermal Units) per hour. When buying a window air conditioning unit, you'll match the square footage of the room to be cooled to the rated capacity of the unit. It's important to pick the right size because an air conditioner that doesn't supply the cooling power needed will leave the room too warm. An oversized unit will cool the space down quickly and turn off. Air conditioners not only produce cool air, but they also remove moisture from the air to lower the humidity. A unit that cycles off quickly may not have enough time to reduce the moisture, leaving the room cool but clammy.

If you're working with an HVAC contractor to install central air, he or she will size the unit for you based on measurements of the house. But if you're picking up a window unit at a home center or hardware store, you're usually on your own. Match room size to BTU output, which is often listed on the package. Be aware of the power requirements for the air conditioner. Most operate on 115/120-volt electrical circuits, the type found in bedrooms and living rooms, but some larger units require a 230/240- volt dedicated circuit.

A through-the-wall air conditioner is an alternative to a window model. They're essentially window units with a more permanent installation. There are also portable units that you can wheel from room to room and must be installed near a window. They include window kits that allow the heat collected by the unit to be exhausted to the outside through a hose. Portable units range from about $250 to $600.

• ​Added to an existing forced-air heating system: $3,500 to $4,000​

If your home is equipped with a forced-air heating system, the type that uses metal ducts to deliver the heat, an HVAC contractor can add a central air conditioner to it. In this type of system, the evaporator that extracts the heat from the air will be installed near the furnace, but the compressor and condenser will be installed in an outside unit. This is called a split system.

An HVAC contractor will size the system based on the size of the house, the amount of insulation, types of windows and other considerations. The contractor may use the term "tons" when talking about the size of the system. One ton of air-conditioning equals 12,000 BTUs.

For the system to work at peak efficiency, it's important that the ducts be sealed. Leaky ductwork can reduce the heating and cooling system's efficiency by up to 20 percent. You or your contractor can apply foil tape designed to seal ductwork or a mastic that you can paint on the seams of the ducts. And any sections of duct that run through an unconditioned space, one that is not heated or cooled, such as an attic or crawl space, should be covered in duct insulation.

If you need to have ducts installed, the cost will be about double what you pay for the cooling unit alone. In these situations, the contractor may install the evaporator in the attic and run the ducts down through closets if possible.

• ​Condenser and one evaporator: $1,000 to $6,000​
• ​Additional evaporators: $400 to $1,000​

In a mini-split system, each room or space to be cooled contains an evaporator, which is hidden in a decorative box that is installed high on a wall or on the ceiling. The evaporator is connected to an outdoor condenser by a small-diameter pipe. This type of system eliminates the need for ductwork, and they're often called ductless air conditioning.

The basic ductless system contains one condenser and one evaporator, but some systems can handle up to five evaporators. As with central air-conditioning, the system should be sized and installed by a qualified HVAC contractor. Mini-splits are operated by remotes, and many mini-split systems can provide heating as well as cooling.

Doing a little air conditioning maintenance helps you get more out of your investment, no matter what type of unit you choose. All air conditioners contain filters to screen out impurities and dust before they reach the system's inner workings. The filters need to be changed or cleaned on a schedule provided by the product manufacturer. The filters for window, portable and mini-splits can be found on the front or top of the inside unit. Central air filters can usually be found at the end of the return duct just before it enters the air handler.