How To Buy Air Conditioners

Cool the rooms that need it the most by choosing the right amount of air conditioner BTUs

Need to cool off? Cooling just one or two of your most frequently used rooms can reduce the load on your whole house unit, which may lead to lower power bills. This guide will tell you which type of air conditioner is best for your home.

Tip: Take note of the voltage of your new unit. UL requires that only 115-volt models using more than 7.5 amps be connected to a standard single outlet. Models that are 208/230 volt require one of three branch circuit power supplies. Keep your home safe and do not exceed the recommended voltage or amps for your electrical circuit.

Window, Freestanding, and Built-In Units

Air conditioners perform three basic functions: lowering the air temperature, removing air moisture, and filtering the air.  

Window Units- Buy Air Conditioners

Window units are the most popular because they are affordable and easy to install. Some models can also double as a heater. Most can be installed in either a single- or double-hung window and typically come with accordion panels to ensure a secure fit. Models designed for sliding windows require a support that can be attached to the exterior of your home.  

Freestanding Portable- Buy Air Conditioners

Freestanding portable air conditioners can be moved between rooms. They have a standard window venting kit for the exhaust, much like a clothes dryer is vented. Most portable units have reservoirs that need to be emptied periodically, although some come with optional hookups for a drainage hose. Other models evaporate much of the moisture as exhaust, greatly reducing the number of times you need to empty the container. Portable units can be heavy and are less efficient than newer window units.  

Built-In Air conditioners- Buy Air Conditioners

Built-in air conditioners can be installed in your wall for permanent placement and can provide both cold and hot air. They are ideal for areas of your house that may not be connected to the central heating and air system, such as a garage. Built-in wall units are more expensive than window units and they require opening a hole in an exterior wall, but they don’t take up window space and allow for a more airtight and secure fit. Larger units may require professional installation.

Mini Spilt  Heating and Cooling- Buy Air Conditioners

If you’re considering a home remodeling project or room addition, mini-split heating and cooling systems can save you the expense of installing ducts, which are necessary for most traditional HVAC systems. Mini-splits are becoming increasingly popular and are a great solution for homes without ductwork.

Cooling Capacity & BTUs

Choosing the right BTU, or British thermal unit, for your room size will make sure get the most energy-efficient cooling system for your home.


The BTU rating is a number that essentially tells you how quickly and effectively a unit can cool a room. Ratings generally range from 5,000 BTUs to more than 20,000.

A unit with too few BTUs may not be able to cool a large space efficiently, while an oversized air conditioner in a small space will cycle on and off, wasting energy and decreasing the unit's ability to adequately dehumidify the room.

It’s important to consider factors such as ceiling height, room insulation, sun exposure, location and your area’s climate when choosing a unit with the right BTU rating.  

Table 6- Buy Air Conditioners
Table 7- Buy Air Conditioners

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Energy Efficiency

All air conditioning units are labeled with their EER (Energy Efficiency Rating). Units with higher ratings offer lower greenhouse emissions and monthly electric bills.

EERs range from 8 to 11.5. The Home Depot carries several models that are Energy Star rated. Check the yellow Energy Guide label on new air conditioners for more information.

Before You Buy Checklist

Homedepot Image
Homedepot Image
Homedepot Image

1. Calculate your room size

2. Check your connections

3. Measure to fit

Multiply the room length by the room width (in feet) to get the square footage of the area to be cooled.

Check out your power source (nearby outlet) and make sure to match the unit to that outlet.

Measure the height and width of the opening and check the dimensions of the AC unit you select to be sure it will fit.