Do you know how AC works?
Air conditioning is one of the greatest modern comforts, keeping homes cool even in the hottest months. But while it may seem like an AC unit simply "makes cold air," it actually works by removing heat from your home and transferring it outside. This process relies on refrigerant, heat exchange, and air circulation.
Understanding how an air conditioner works can help homeowners make smarter decisions about maintenance, efficiency, and energy use. Given that heating and cooling account for nearly 50% of the average home's energy use, according to the U.S. Department of Energy (DOE), knowing the basics of your AC system can even save you money.
Most homeowners probably can’t explain how their air conditioning system works. But understanding the process helps you make good decisions.
Here’s how air conditioning really works.
Step 1: Pulling Warm Air from Your Home
The cooling process begins when the blower fan in the air conditioner pulls warm indoor air through return vents. As this air enters the system, it passes through a filter that traps dust, pollen, and other airborne particles, improving indoor air quality.
Once the air is inside the system, it moves toward the evaporator coil, where the real cooling begins. This coil contains refrigerant, a special liquid capable of absorbing heat. Most modern ACs currently use R-410A refrigerant, which replaced older, ozone-depleting substances like R-22.
However, starting January 1, 2025, new air conditioning systems will transition to R-454B and R-32 refrigerants. These next-generation refrigerants have lower global warming potential (GWP) than R-410A, aligning with environmental regulations aimed at reducing greenhouse gas emissions. Homeowners purchasing a new AC system after 2025 will have units that use these environmentally friendly refrigerants.
No matter what kind of air conditioning system you have, they work on the same principle. whether it’s a central AC, a window unit, or a ductless mini-split. In a central AC system, the air is pulled through ducts and cooled in an indoor air handler before being redistributed. In contrast, a window AC has an evaporator coil built into the unit itself, cooling the air right inside the room.
Step 2: Absorbing Heat with Refrigerant
After the warm indoor air is pulled into the vents and through the filters, it passes over the evaporator coil, and the refrigerant inside the coil absorbs the heat. This causes the refrigerant to evaporate from a liquid into a gas, carrying the heat away from the air. The now-cooled air is then pushed back into the home through ductwork or directly from the unit.
At this point, the refrigerant has done its job absorbing heat, but now it needs to get rid of that heat somewhere. That’s where the outdoor unit comes in.
Step 3: Moving Heat Outside
The gaseous refrigerant, now carrying the heat from inside your home, travels through copper tubes to the outdoor unit. Here, the compressor increases the pressure of the gas, making it even hotter. This might seem counterintuitive—why make the refrigerant hotter? But this step is crucial because it allows the heat to be released efficiently once the refrigerant reaches the condenser coils.
Sometimes referred to as the "heart" of the system, the compressor keeps the refrigerant moving through the entire AC cycle. This is a vital part of both central AC systems and mini-split units, while window and portable ACs have a built-in compressor to handle the same process on a smaller scale.
Step 4: Releasing the Heat Outside`
Once the high-pressure refrigerant reaches the condenser coils in the outdoor unit, a large fan blows air across the coils, allowing the heat to dissipate into the surrounding environment. As the heat is released, the refrigerant cools down and turns back into a liquid, ready to cycle back inside and absorb more heat.
Efficiency is key at this stage. Studies show that dirty or blocked condenser coils can reduce system performance by up to 30%, according to Energy Star. That’s why regular cleaning and maintenance are essential to keeping an AC unit running at peak efficiency.
ServiceOne Air Conditioning and Plumbing offers ClubOne Memberships that provide twice a year scheduled maintenance for your AC system. Plumbing maintenance plans through ClubOne are also available.
Step 5: Circulating the Cool Air Back Into Your Home
Now that the heat has been removed, the system pushes the newly cooled air back into your home. In a central AC system, the blower fan sends this air through ductwork, distributing it to every room. In a ductless mini-split, a fan inside the wall-mounted unit blows the cooled air directly into the room, while window and portable ACs do the same within a limited area.
Proper airflow is essential for efficiency. An air conditioner can only work effectively if vents remain unblocked and filters are regularly cleaned or replaced. Studies show that proper maintenance can reduce AC energy consumption by 15%, lowering energy bills and extending the unit’s lifespan.
Step 6: The Thermostat Keeps Everything in Check
All of these steps repeat until your home reaches the desired temperature, which is controlled by the thermostat. Once the thermostat senses that the indoor temperature has dropped to the set level, it signals the AC to take a break. If the temperature rises again, the system kicks back on, ensuring continuous comfort.
A smart thermostat takes this process to the next level by learning household patterns, adjusting temperatures automatically, and allowing remote control via smartphone apps. These thermostats use sensors, Wi-Fi connectivity, and machine learning algorithms to optimize cooling efficiency. Some models even integrate with weather forecasts to pre-adjust temperatures or detect when the home is unoccupied to save energy.
Research shows that smart thermostats can reduce cooling costs by 10-12% by minimizing unnecessary energy use. Some popular models have features such as voice control, geofencing, and detailed energy usage reports, making them a great addition for homeowners looking to enhance efficiency and comfort.
How Different AC Systems Accomplish the Same Goal
While all air conditioners follow the same basic process, different types of AC systems use different methods to achieve cooling:
Central Air Conditioning is the most efficient way to cool an entire home. It uses an outdoor compressor/condenser unit paired with an indoor evaporator coil and air handler, delivering cooled air through ducts. However, for best performance, ducts must be properly sealed, as leaky ducts can waste 20-30% of conditioned air.
Ductless Mini-Splits work similarly to central AC but don’t require ductwork. Instead, individual indoor units cool specific rooms, making them ideal for homes without ducts, home additions, or areas that need zoned cooling.
Window Air Conditioners are compact, self-contained units that cool a single room by pulling in warm air, passing it over an evaporator coil, and expelling heat through the back of the unit.
Portable Air Conditioners are similar to window units but designed to be moved between rooms. However, they are often less efficient because they require venting through a hose, which can allow some heat back into the room.
Geothermal Heat Pumps take a different approach by transferring heat into the ground, which maintains a stable temperature year-round. Though more expensive to install, these systems are up to 50% more efficient than traditional air conditioners.
ServiceOne is Here to Help!
No matter the kind of air conditioning system you have, or even the age of the system you have, they all work in the same way. The newer the unit, the more efficient it will be, but older units work on the same fundamental principles as brand new ones. Understanding how your AC works can help you make smarter decisions about maintenance, energy efficiency, and troubleshooting—ensuring your system keeps you cool for years to come.
ServiceOne is here to answer your questions and solve your problems with air conditioning, heating, or plumbing. Call us. We’ll keep you comfortable!