The 4 Main Types of Air Conditioners

split level air conditioner

When it comes to chilling out, nothing beats an air conditioner on a hot day. It’s fair to say, though, not all air conditioners are created equal.

If you’re trying to wade through information on air conditioner systems and find a unit that’s right for your space, we’ve got the details you need.

Factors in Deciding What Type of AC Is Best

There are several things to consider when deciding on the right air conditioner type for your home, including the style and availability of windows, your budget, and whether you own or rent your home.

Some AC units require windows for venting or even mounting the unit. The type of window you have can greatly affect the type of unit that is suitable for the space.

Budget is always a factor in home improvement decisions, and it’s no different when deciding on the best type of AC unit for your house. Centralized AC can run $7,000-16,000 so it’s no small investment. Small window units, on the other hand, cost a few hundred dollars.

If you’re renting, you’ll need to see what’s allowed via your rental contract. It’s fair to assume you won’t be installing comprehensive AC units unless you own the home.

In addition, consider the climate where you live. Features on some types of air conditioning units are better matched to humid environments, for example.

If you live in a hot, arid region like the southwest, you should get an evaporator cooler. If you live in a different region, a compressor-driven air conditioning system is the best choice.

Noise is another significant factor in your final decision. If the hum of the AC unit will distract you, find a unit that runs quietly.

Understand BTUs to Calculate What Size AC Unit You Need

free standing AC unit with box near cat

A BTU is an acronym that stands for British Thermal Unit. It’s a measurement of energy. Every AC unit will be marked with a BTU capacity, ranging from around 5,000 BTUs (enough to cool a small room) to capacities as high as 12,500 BTUs.

Even more important than the types of air conditioners you choose, BTUs are the best way of matching an air conditioner to your space.

A unit with low BTUs for the space will fail to help you keep your cool on hot days and will not run efficiently. On the other hand, an oversized unit will add too much moisture to the air.

Since BTU is the cooling capacity of the unit, this is more important than the horsepower. However, you can determine the efficiency of the unit by dividing the watt rating into the BTU output.

The unit must have an energy efficiency rating (EER) of at least 9.7 for models under 8,000 BTU/hr and 9.8 for larger models. The most efficient models have an EER of 11 and higher. Each model should have its EER clearly marked.

Another measurement of efficiency to consider is the SEER rating, which stands for Seasonal Energy Efficiency Ratio. This is a lab-reported measurement of how the unit is expected to perform throughout the varying temperatures of an entire season.

It’s a helpful tool in making your decision, especially for expensive units. Most people recommend purchasing a central air conditioner with a SEER rating higher than 12.0.

In most cases, you don't need to buy an air conditioner with more than a 14 SEER rating, and almost never higher than 16 SEER.

How Do AC Units Work?

outdoor AC compressor

Every air conditioning unit has the same basic components, which include the compressor, thermostat condenser, evaporator, and fan, among others.

The compressor is controlled by an internal thermostat. As the thermostat detects warm air, it activates the compressor.

The compressor circulates a refrigerant gas, increasing the pressure and temperature of the refrigerant as it compresses it through a series of pipes. The refrigerant then moves to the condenser for further processing.

In the condenser, a cooling system removes heat from the high-pressure gas, and the gas changes phase to become a liquid. This chilled liquid is pushed through tubing until it reaches the evaporator system.

Inside the home, the evaporator fan collects warm air and passes it through a chamber containing the chilled liquid refrigerant.

The fan system blows this air, which has now been cooled, back into the room, lowering the overall temperature of the space.

If the thermostat still detects air that is warmer than desirable, the process continues, and the refrigerant and any excess heat that remains in the system are passed back to the compressor in order to begin the cycle again.

1. Window AC Units

window AC unit

If you’re looking for an AC unit for a room, the ubiquitous window unit is a quick and easy solution for cooling a small space.

When selecting a window unit, consider the size of the space you intend to cool and match it to the BTUs of the unit.

Window air conditioners come out of the box ready to work. However, installing window AC units may require two people for safety. All of the components are usually inside the unit, so you won’t have to install any additional parts outside the home.

2. Portable AC Units

ductless AC unit

Portable air conditioners function in much the same way as window units. They are self-contained and ready for quick installation. The true benefit to the portable unit is, well, portability. Easily move it from the bedroom to the den as the need arises.

Portable air conditioners are typically a bit more expensive than traditional window units, likely due to this convenience.

Portable air conditioners are most effective for a single room or space that is not more than about 450 square feet.

To install a portable air conditioner, simply place it near a window. Run the hose from the back of the unit into the frame of the window. All types of air conditioners must have access to outside air so do not run your air conditioner without first taking this step.

Secure the hose into the window frame with the hardware included. Then fill any gaps around the hose, plug it in, and turn the unit on.

3. Central Air

outdoor AC compressor

Both window and portable air conditioners are great options if you rent your space. If you are a homeowner and want a long-term solution, however, you may want to invest in central air conditioning.

This can come in the form of a heat pump or be an add-on to your existing furnace.

Either way, you will have a separate unit either on the roof or near the foundation that draws, filters, and returns the cooled air to your home.

These units are exponentially more expensive, costing many thousands of dollars, in contrast to a few hundred. However, they are also highly efficient, convenient, and invisible indoors compared to the clunky and space-consuming portable or window options.

Central air is less efficient than more targeted methods of AC, due to the cost of pumping it through the system. It’s also less efficient in the fact that you’re paying to cool the entire space, when you may not need that much coverage.

However, central AC is by far the most convenient form of air conditioning.

To operate, it simply requires pushing a few buttons on the wall thermostat. It creates a temperature-controlled atmosphere throughout the house, without wide variations from one room to another.

4. Ductless AC

split AC unit in wall

If your home doesn’t have ductwork, air conditioning called ductless, or mini-split, systems can be installed. This type of system provides units inside the home in the rooms where they are needed, rather than a central system that is “hardwired” in.

However, the compressor and condenser unit remains outside like with the central air conditioning system, in contrast to the self-contained window or portable units. The indoor portion contains the evaporator and fan.

Ductless units are mounted to the wall and basically work as a fan to blow the cooled air into the room.

Tubing connects the indoor and outdoor units and circulates refrigerant between them. There is no ductwork to install or maintain, which not only makes the job easier, but less expensive.

Not having air travel through ductwork also makes the unit more energy-efficient since there is less energy loss. Ductless air conditioners also eliminate the heat that often leaks in around window and portable units.

For individual spaces, ductless units offer an efficient way to cool without invasive installation. However, a single unit is not a cost-effective or efficient way to cool an entire house.

You can install ductless units in several spaces throughout the home, each connecting to the compressor outdoors. As a system, it adequately cools a larger space.

There are several other advantages to a split, or ductless, AC. For example, the unit itself doesn’t have to be removed during the winter, like most portable and window units.

In fact, they’re quite weather-resistant so there’s no need to worry when it rains or snows.

Another advantage of a split unit AC system is that you can create zones within your home. This significantly increases efficiency. Rather than paying for the central AC to pump through the entire house, a ductless AC unit can be turned on in a single space for targeted cooling.

Air Conditioner Maintenance

fan in AC unit

Regardless of the type of AC unit you decide on, there will be some maintenance to perform. Smaller AC units last an average of 10 years, with proper care, while centralized AC units can last 10-20 years, so it’s worth making sure they are well maintained.

Many portable units have a drip pan that will need to be emptied regularly. Read your owner’s manual to see if this is true for your unit.

Most AC units have filters that need to be cleaned or replaced regularly. Some units have more than one. Know how to access and care for the filters. It’s the fundamental component of good AC care.

Check out this information for a more comprehensive look at How to Service and Maintain Your Air Conditioner.

Like most technology, options for cooling are ever-evolving. It wasn’t too many years ago that heat pumps were introduced as an efficient way to both heat and cool with the same unit.

Geothermal systems are also growing in popularity as a way to draw air from beneath the surface of your yard, taking advantage of the natural heat of the planet to warm your home, and returning hot air from the home when cooling is needed instead.

Geothermal is an expensive option to install, but it's ultra-efficient, sustainable, and long-lasting.

When selecting an air conditioning system for your home, be aware of the square footage of the space, whether that be a single room or the entire home. Also check out the warranty for any model you buy and weigh the pros and cons of features such as fan delay and variable speed motors.

Whatever type of unit you decide on, be sure to perform regular maintenance to your air conditioning system to keep it in optimal functioning condition.