How Do Air Conditioners Work?
Air conditioning systems work by absorbing heat and humidity from your indoor air and transferring it outside, returning chilled air to keep your home comfortable. They achieve this continuous cycle by using a chemical called refrigerant, which shifts between liquid and gas states across a specialized system of coils.
On July 17th, 1902, Willis Carrier invented the first modern air conditioning system. Carrier’s groundbreaking invention helped give rise to numerous industries that continue to power our economy today. Today’s modern cooling systems still operate on the same basic principles, providing comfortably chilled, reliable air to people inside. So, how do air conditioners work exactly?
Air conditioners come in a variety of shapes and sizes, but they all operate on the same basic premise. An air conditioner provides cold air inside your home or enclosed space by actually removing heat and humidity from the indoor air. It returns the cooled air to the indoor space and transfers the unwanted heat and humidity outside.
A standard air conditioning system works by using a specialized chemical called refrigerant, and has three main mechanical components: a compressor, a condenser coil and an evaporator coil. These components work together to quickly convert the refrigerant from gas to liquid and back again. This process involves five steps:
- The compressor raises the pressure and temperature of the refrigerant gas and sends it to the condenser coil where it is converted to a liquid.
- Then the refrigerant travels back indoors and enters the evaporator coil. Here the liquid refrigerant evaporates, and cools the indoor coil.
- A fan blows indoor air across the cold evaporator coil where the heat inside the home is absorbed into the refrigerant.
- The cooled air is then circulated throughout the home while the heated evaporated gas is sent back outside to the compressor.
- The heat is then released into the outdoor air as the refrigerant returns to a liquid state.
This cycle continues until your home has reached the desired temperature, offering you quiet, efficient comfort.
How Does Air Conditioning Work To Cool Your Home?
Many homes in North America rely on split-system air conditioners, often referred to as “central air.” Central air conditioning systems include a number of components and do much more than just cool the air inside. Engineered for advanced comfort, they also can control humidity, improve air quality, and manage airflow seamlessly within your home. So before we answer the question of how do air conditioners work, it will be helpful to know what makes up a typical system.
What Are the Main Parts of a Central Air Conditioning System?
A central air conditioning system (or split-system) is a cooling network that uses an indoor unit to distribute cold air and an outdoor unit to release absorbed heat. It relies on a thermostat, connected ductwork, and refrigerant lines to maintain a comfortable indoor environment.
A typical system normally includes the following:
- a thermostat that controls system operation
- an outdoor unit that houses a fan, condenser coil and compressor
- an indoor unit (typically either a furnace or air handler) that houses the evaporator coil and fan to circulate the cooled air
- copper tubing that allows refrigerant to flow between the indoor and outdoor units
- an expansion valve the regulates the amount of refrigerant going into the evaporator coil
- ductwork that allows air to circulate from the indoor unit out to the various living spaces and back to the indoor unit
In its most basic description, the air conditioning process involves two actions that occur simultaneously, one inside the home and one outside the home.
- Inside the home (sometimes referred to as the “cold side” of the system), warm indoor air is cooled as it blows across a cold cooling coil full of refrigerant. The refrigerant is first expanded to drop the pressure and then heat from indoor air is absorbed into the refrigerant as the refrigerant turns from liquid to gas. The cooled air is distributed back to the house.
- Outside the home (sometimes referred to as the “hot side” of the system), the refrigerant gas is compressed before entering a large coil in the outdoor unit. Heat is released outside as the refrigerant turns back to a liquid and a large fan pulls outdoor air through the outdoor coil rejecting the heat absorbed from the house.
The result is a continuous cycle of heat and humidity being removed from indoor air, cool air returning to the home, and heat and humidity exiting the home.
How Does an Air Conditioner Work Step-by-Step?
An air conditioner works step-by-step by utilizing a thermostat to trigger a cycle where warm indoor air is pulled over cold, refrigerant-filled coils, absorbing the heat. The system then pumps the heated refrigerant outside to release the thermal energy, while blowing the newly chilled air back into your living spaces.
Now that you have a basic understanding of how air conditioners work, let’s dig a little deeper and describe the entire AC cooling process:
- The thermostat, which is typically mounted on a wall in a central location within the home, monitors and controls the temperature of the indoor air. Smart home integration allows many modern thermostats to optimize this for maximum energy efficiency.
- The AC cooling process starts when the thermostat senses the air temperature needs to be lowered and sends signals to the central air conditioning system components both inside and outside the home to start running.
- The fan from the indoor unit pulls hot air from inside the house through return air ducts. This heat from the air passes through air conditioner filters where dust, lint and other airborne particles are collected, improving your home's air quality.
- The filtered, warm indoor air then passes over cold evaporator coil. As the liquid refrigerant inside the evaporator coil converts to gas, heat is absorbed from the indoor air into the refrigerant, thus cooling the air as it passes over the coil.
- The indoor unit’s blower fan then pumps the chilled air back through the home’s ductwork out into the various living areas.
- The refrigerant gas leaves the home through a copper tube and passes into the compressor in the air conditioner unit outside.
- Think of the compressor as a large electric pump. The compressor pressurizes the refrigerant gas and sends the refrigerant into the outdoor unit’s condenser coil.
- A large fan pulls outdoor air through the condenser coil, allowing the air to absorb heating energy from the home and release it outside.
- During this process, the refrigerant is converted back to a liquid.
- It then travels through a copper tube back to the indoor unit where it passes through an expansion device, which regulates the flow of refrigerant into the evaporator coil.
- The cold refrigerant then absorbs more heat from the indoor air and the cycle continues.
Jennifer Fletcher, owner of Modern Air Solutions in Gurnee, IL, explains an air conditioner to homeowners in simple terms: its main job is to remove humidity from the air.
“The drier the air is, the more comfortable you feel — even at higher temperatures. As the system pulls moisture and heat out of your home, it delivers that crisp, cool comfort people associate with good air conditioning.”
How Do Different Types of Air Conditioners Work?
Different types of air conditioners work by utilizing the same core refrigerant cycle, but they vary in how they deliver the cooled air to your space. Split-systems use ductwork for whole-home comfort, packaged systems house all parts in a single outdoor cabinet, and ductless systems provide targeted, room-by-room climate control without relying on ducts.
Because indoor living spaces come in a variety of shapes and sizes, from today’s new tiny homes to large estates, residential air conditioning systems are available in different styles. There are three primary types: split-system, packaged, and ductless air conditioners. Each has its own specialized uses. The best air conditioner for you depends on your geographical location, the size and physical limitations of your home, and the way you use it.
How Does a Split-System Air Conditioner Work?
A split-system air conditioner separates its components into an indoor air handler and an outdoor condenser unit, connected by refrigerant lines. This setup is best suited for homes that want consistent, whole-home cooling utilizing existing ductwork.
Split-systems offer the most common answer to the question, “what is central air?” The indoor unit, typically a furnace or an air handler, includes the evaporator coil and blower fan (air handler) that circulates air throughout the home. The outdoor unit holds the compressor and the condenser coil.
Split-system air conditioners provide a variety of options, including basic single-stage systems, quieter and more efficient two-stage systems, and the quietest, most energy-saving inverter air conditioners. A split system air conditioner offers reliable temperature control to the entire home. Because the system uses filters in the indoor air handler, it can clean your air while it cools it. Learn more about what is a split air conditioning system?
How Does a Packaged AC System Work?
A packaged AC system houses the evaporator coil, blower fan, compressor, and condensing coil entirely within one outdoor unit. This configuration works best when a home lacks the interior space—such as an attic or closet—required for a split-system indoor unit.
Like split systems, packaged systems pull warm air from the home, through return air ducts, into its evaporator coil section. The air passes over the evaporator coil and the cooler air returned back to the home through supply air ducts. And, as with a split system, the unwanted heat is released to the outside through the condenser coil.
Packaged air conditioning systems also offer a variety of options to provide better energy efficiency. They are available in two-stage systems and single-stage systems. Higher efficiency models include multi-speed blower fans. In the United States, packaged systems are most common in the south and southwest areas of the country.
How Does a Ductless AC System Work?
A ductless AC system works by connecting a single outdoor condenser to one or more indoor wall, ceiling, or floor-mounted blowers via small refrigerant lines. Ductless systems are ideal for targeted room cooling, room additions, or historic homes where installing traditional ductwork is impossible or too invasive.
These are not considered to be central air systems because they deliver cooling to specific, targeted areas. In a ductless system, each indoor unit is designed to provide cool air only for the room in which it is installed. Some ductless systems can include multiple indoor units connected to one outdoor unit. The indoor unit contains an evaporator coil and blower fan to pull warm air from the room, across the cool evaporator coil, then return the cooler air back into the room. Refrigerant runs through the copper tubing to the outdoor unit where the compressor and condenser coil are located. Heat from inside is released through the outdoor condenser coil.
These flexible systems deliver pinpointed comfort in the areas where indoor units are placed. They also act like a zoning system by offering individual temperature control over each separate room. For example, if you want a cooler home office but a warmer bedroom, install a ductless unit in each room.
Knowing the answer to “how do air conditioners work?” can help you choose a system for AC installation that makes the most sense. Contact your local Carrier dealer today to schedule an appointment and get a quote for central air conditioner price.
Frequently Asked Questions
Air conditioning is a system that cools, dehumidifies, and circulates air in indoor spaces to maintain a comfortable temperature. It works by removing heat from the air and transferring it outside using a refrigerant, while also filtering and controlling humidity levels.
On July 17, 1902, Willis Haviland Carrier designed the first modern air-conditioning system, launching an industry that would improve the way we live, work and play.
Air conditioners generally do not use outside air for cooling the interior of your home. Air conditioning systems recirculate indoor air. The air is cooled by passing over the evaporator coils inside the indoor unit and then distributed back into the house through ductwork. The outdoor unit expels the heat absorbed from the indoor air but does not bring in outside air.
An air conditioner cools a room by circulating refrigerant through a cycle of evaporation, compression, condensation, and expansion. The refrigerant absorbs heat from indoor air at the evaporator coils, releases it outside at the condenser coils, and then cools back down before repeating the process.
A smart thermostat improves your air conditioning system by learning your schedule and automatically adjusting the temperature for optimal efficiency. This intelligent integration ensures your system doesn't waste energy cooling an empty house, resulting in significant long-term reductions in your energy bills.
Quiet operation ensures that your advanced HVAC system maintains a peaceful home environment without disruptive mechanical noises. Modern inverter technology and specialized sound-dampening components allow today's air conditioners to operate as quietly as a whisper, improving your overall comfort.
Instead of simply turning the AC off all day when you aren’t home, it’s more cost-effective to leave the air conditioner on but adjust the temperature about 7-10 degrees higher. Running the AC continuously at a lower temperature uses more energy, increasing your heating and cooling bill. Smart thermostats can optimize cooling by adjusting the temperature when you're not home, leading to energy savings.
An air conditioner works by pulling warm air from a room, passing it over cold evaporator coils filled with refrigerant, which absorbs the heat. The refrigerant is then pumped to the condenser outside, where it releases the heat. The cooled air is circulated back into the room, and the process repeats.
About The Author: Ryan Mayes is a Senior Digital Brand Marketing Manager at Carrier who focuses on creating clear, helpful resources on HVAC topics. Ryan’s goal is to guide readers toward smart, confident decisions about their indoor comfort.