How to select the best air-conditioning system for your home

How much power do you need from your air conditioner?

Before buying an air conditioner for your home or apartment, it’s important to determine how much cooling power you’ll need. Cooling capacity is measured in British Thermal Units (BTUs), which indicate how much heat a unit can remove from your space.

To estimate the right BTU rating, consider the size of the area you want to cool, ceiling height, insulation, sun exposure, and how many people typically occupy the room. For example, a small bedroom may need a 5,000–6,500 BTU unit, while a larger living area could require 10,000 BTUs or more. If your room is very sunny, add 10% to the recommended BTU; if it’s heavily shaded, subtract 10%. For each additional person beyond two, add 600 BTUs. If the unit will be used in a kitchen, add 4,000 BTUs.

A BTU calculator can help you determine the appropriate capacity for your space. Choosing the right size ensures efficient cooling and helps avoid wasted energy or poor humidity control.

When selecting an air-conditioning system, there are four main types to consider. Below, we outline the pros and cons of each to help you decide which is best for your home.

Window air-conditioners

Window air conditioners are a popular and cost-effective choice for cooling single rooms or small spaces. Designed to fit into a window, these units contain all the necessary components—compressor, condenser, expansion valve, and more—in one package. Some models are made specifically for casement windows that swing open from the side.

Window units are generally affordable and offer good cooling power for their size. They’re also relatively easy to install and don’t require permanent modifications to your home, making them ideal for tenants. However, you’ll need to seal any gaps around the unit to prevent air leaks and maintain efficiency.

One advantage is portability: you can remove the unit and take it with you if you move. Keep in mind that window air conditioners may take longer to cool rooms with open layouts or multiple connected spaces, and they need to be removed or covered during the winter months in colder climates.

Portable air-conditioners

Portable air conditioners offer flexibility and are easy to set up, making them a good option for renters or spaces where window or wall units aren’t practical. These units sit on the floor and use a hose to vent hot air out a nearby window. An adjustable frame helps seal the window opening around the hose.

While portable units can be moved from room to room, they tend to be bulkier and take up valuable floor space. They are typically heavier and can be difficult to roll on carpeted surfaces. Portable air conditioners are generally less efficient and noisier than window or wall units, and they often use more energy for the same cooling output.

Dual-hose models are more efficient than single-hose versions, as they use outside air to cool the unit, but they are also more expensive. Regardless of type, portable units don’t require permanent installation or wall modifications, which is helpful for renters. Be aware that you may need to empty a water collection tray or tank, depending on the model.

Ductless/Split air-conditioners

Ductless or split air conditioners are a sleek and efficient solution for cooling larger areas or multiple rooms. These systems consist of two main parts: an indoor unit mounted on the wall and an outdoor condenser. The two are connected by hoses that carry refrigerant and power.

Installing a ductless system requires drilling holes in your wall to run the hoses, so professional installation is recommended. While these systems are more expensive than window or portable units, they offer powerful, quiet cooling and can be expanded to cool several rooms by adding more indoor units. Ductless systems are especially useful in homes without existing ductwork or in spaces where adding ducts isn’t practical.

Keep in mind that the cost can increase if you need multiple indoor units for different rooms. However, ductless systems are often more energy efficient and visually appealing than other options.

Wall air-conditioners

Wall air conditioners are similar to window units but are installed directly into an exterior wall. This requires cutting a hole in the wall, so it’s important to be aware of the location of studs, copper pipes, and electrical wiring. Professional installation is often recommended to ensure safety and proper sealing.

Wall units are more efficient than portable air conditioners and often outperform window units due to their tighter seal. While the upfront installation is more involved, the long-term energy savings can offset the initial cost. Wall air conditioners are a good choice for homeowners who want a permanent solution and don’t want to block a window.

If you rent your home, you’ll need your landlord’s permission before making any structural changes (see our guide to landlord responsibilities for rental-unit repairs). Wall units are typically left in place year-round and don’t need to be removed for winter.

With this overview of air-conditioning options, you’re ready to choose the system that will keep your home cool and comfortable all summer long—no matter how high the temperature climbs!

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