What Is HVAC? How Does HVAC Work?

Kelly Weimert
Written by Kelly Weimert
Updated April 10, 2023
A woman and young girl relax on a couch enjoying the air conditioning
Photo: Fizkes / Adobe Stock

Home is where the heat and AC are

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If you want to feel comfortable in your home in any weather, you might need to get up close and personal with your HVAC. But what is HVAC and how does it work? Whether you’re a new homeowner, trying to decide on installing a new HVAC unit, or just wondering about HVAC maintenance—knowing your system is essential to staying cool. 

No matter what climate you live in, you’ll need an HVAC unit to keep the airflow in your home comfortable during what HVAC pros call heating and cooling seasons.

What Does HVAC Stand For? 

The term “HVAC” stands for heating, ventilation, and air conditioning—an umbrella category to describe the heating and air conditioning systems in your house. It also encompasses the role mechanical or natural ventilation plays in keeping your house at the ideal temperature and humidity.

Though these systems are collectively called HVAC for short, you might also hear them called an HVAC system or HVAC unit. All of these names are really blanket terms for the combination of three systems—heating, cooling, and ventilation—that work to keep your house at a comfortable temperature and control the indoor air quality. 

Not only are HVAC systems used in your home, but they’re also everywhere you look, from residential or commercial buildings to airplanes and even cruise ships.

How Does an HVAC System Work?

At a basic level, HVAC systems work by drawing in cool air through the ventilation system, heating the air, and then redistributing it throughout your home—or vice versa with cool air. No matter what type of HVAC system you have, the components have the same functions. However, HVAC systems can work in several different ways depending on the type of system you have.

Air Conditioning Systems

Air conditioning systems transfer heat and humidity from inside a home to outside, cooling the indoor environment. AC units use refrigerant, which is compressed to increase the refrigerant's pressure and temperature before it flows to a condenser. Once it reaches the condenser, the heat from the refrigerant is released outside of the home and the refrigerant itself is condensed back into a liquid. 

Finally, the refrigerant goes through a pressure-lowering valve, which cools it, allowing it to evaporate and once again absorb indoor heat. At this point, the cold refrigerant returns to the compressor and the process repeats itself to continue cooling the home. 

Heat Pumps

Heat pumps work similarly to air conditioners, but they can heat a home as well as cool it. Like air conditioners, heat pumps use compressed and condensed refrigerant to absorb heat from one area and transfer it to another. 

During the cool months, the heat pump can trap heat from outside and transfer it inside the home—even when it's cold outside, there's enough heat energy for the refrigerant to grab and transfer inside. In the warmer months, the process can be reversed, with the refrigerant transferring indoor heat outside to cool the home. 


Unlike heat pumps and air conditioners, furnaces can't cool a home; they're only used for heating. They traditionally use a fuel source, like oil or propane, to create heat and distribute it throughout the home using the home's vents and ductwork. 

However, there are also electric furnaces, which use an electrical current to warm up the indoor air. Electric furnaces are usually more energy efficient and less expensive to install than gas furnaces, but they're not quite as effective as gas furnaces at heating homes during really cold outside temperatures. 

In combination, these systems keep your home comfy all year round. Your thermostat acts as the command center for your HVAC unit, giving you the ability to adjust the temperature as needed. 

There are a large number of electrical components needed to keep these systems running. 

What Is Included in an HVAC System?

A person adjusting a ceiling vent for an HVAC system
Photo: The Toidi / Adobe Stock

The three components that make up your HVAC come with all sorts of different equipment. Though many of these components will come as part of purchasing an HVAC system, there are times when you may need to buy or replace just one of the many types of equipment below.

Heating Equipment  

Heating systems are as varied as they are complex. Here are some common HVAC parts you might need to use or replace to keep your home warm and cozy. 

  • Boilers: These heaters warm water using gas propane or electricity. Boilers are often found in older homes, but are actually very efficient heating systems. 

  • Radiators: If your system has a boiler, it likely also has radiators. Radiators contain heated water which heats the air in your home. 

  • Pipes: For systems with a boiler, pipes aren’t just for plumbing. They transport water to your radiators and help keep your home toasty. Pipes are also the main heat source for radiant heating systems. 

  • Furnaces: Your furnace directly heats the air with a heat exchanger and is extremely versatile. Furnaces can be fueled by a number of methods, including electricity, natural gas, propane, oil, or even geothermal energy.  

  • Blower motors: These motors are used in forced air systems. Blower motors deliver warm air via your ductwork. Blowers also play an important role in the cooling component of some HVAC systems. 

Ventilation Equipment

Ventilation equipment exists in many heating and cooling systems. Here are some key types of equipment you might need to replace or maintain to keep your systems running efficiently. 

  • Ducts: Ductwork is always present in forced-air systems. It’s built into your home and is used to transport both hot and cold air throughout your house. Well-built ductwork is the key to keeping air circulating through your home. 

  • Vents: Wall, floor, and ceiling vents are the entry point from your duct system into your living space. The word “vent” itself has multiple meanings and can apply to any mechanism that allows hot or cold air to be transferred between different areas. For example, there are vents that allow excess heat to exit your home and keep your inside temperatures cool.

  • Chimneys or flues: Often seen with forced-air systems, chimneys or flues are used to vent hot combustion or exhaust gasses away from the home. 

  • ACV vents: ACV vents work similarly to chimneys, but are used with more modern high-efficiency furnaces where gas temperatures are cooler. You may also see vents made of other similar heat-resistant materials.

What Is the Difference Between AC and HVAC?

As we discussed above, HVAC stands for heating, ventilation, and air conditioning. The main difference between the terms “AC” and “HVAC” is that, in general, AC refers to the cooling system in your home and not the heating component encompassed in an HVAC. That said, you might hear these terms used interchangeably. In addition to cooling things down, central air conditioning includes an air filtration system that also regulates the air quality in your home.

Common Types of HVAC Systems

Two outdoor air conditioning units for an HVAC system
Photo: Christian Delbert / Adobe Stock

Today, there are lots of different combinations you can configure when purchasing an HVAC system that handles both heating and cooling. We’ll walk you through the four most popular types, as a jumping-off point.

1. Split Systems 

A split system is a type of forced-air system, and it’s one of the most common types of HVAC units. This type of system has a unit for cooling the air and another for heating it.

The location of the cooling and heating systems in these types of units are, true to their name, split. The main components of the cooling system are outside of the home. They use refrigerant to cool the air, and a blower motor, fans, and ductwork to distribute the air in your home. You may notice these outdoor units buzzing near homes or businesses.

The heating unit of a split system is inside the house. Your furnace heats the air and then spreads it through the house in a similar fashion using your blower motor, fans, and ducts.

Typical cost: $3,800 to $7,500

Who is this best for?: This is an ideal system for most homes. A split system provides the power a homeowner needs in any climate. This is a huge plus for areas with both extremely hot summers and very cold winters.


  • Provides comfortable temperatures in both summer and winter

  • Customizable to fit your needs 

  • Fairly low maintenance


  • Can be a bit noisy

  • Installation can be more involved than other systems, especially in homes without ductwork

2. Ductless Systems 

A ductless or duct-free system has individual HVAC units in each room of the house rather than two larger units. You might also hear this system referred to as a mini-split system. 

Initial installation costs of ductless systems can be more expensive, but the benefit is you can control the temperature in specific rooms. You might see these systems installed in businesses or homes where individual room temperature control is desirable—for example, hotels or commercial buildings like offices. 

These systems are also more efficient, potentially saving you big on energy costs in the long run.

Typical cost: $2,000 to $14,500

Who is this best for?: This system is best for homeowners who want to control temperature room to room.


  • Allows for more specific temperature control in each room

  • More energy-efficient than many other systems

  • May be quieter than traditional systems


  • Installation may be more costly than other systems

  • Requires more maintenance, as each unit has its own filter

3. Hybrid Systems

Hybrid or hybrid-split systems are set up similarly to split systems. They also function in a similar way. The defining difference is that a hybrid system can switch between using gas and electricity. This improves energy efficiency, so you can be good to the planet and your wallet.

A hybrid system switches between using a traditional furnace and a heat pump. A heat pump system pulls air through a heat exchanger, which saves power by using the electricity already running through your home to heat the air. A blower then pushes this heated air through the ductwork in your home. 

Typical cost: $2,500 to $10,000

Who is this best for?: If you live in a climate that typically doesn’t experience extreme temperatures, you can take advantage of a hybrid system and use the fuel source that will be most efficient during each season.


  • Can switch between power supplies to be more efficient

  • Can be set to switch automatically at certain temperatures 

  • Efficient and flexible for areas with a range of temperatures


  • Installation can be pricier for this option

  • Very cold climates can mean these systems aren’t as energy-efficient in the winter

4. Packaged Heating and Air Systems

A packaged heating and air system is a less common type of HVAC system. These systems typically are installed as high as possible in the structure, and act as one contained unit which produces both heating and cooling.

These systems are much smaller than other HVAC systems and run relatively efficiently. The downside is that the heating system often does not run as well as the cooling system. 

Recent technological advancements have made some packaged heating systems, like heat pumps, more efficient. Because of this, packaged heat systems have potential as good future options for homes in colder climates.  

Typical cost: $10,000 to $14,000

Who is this best for?: Because the heating function of these systems isn’t as powerful as other HVAC systems, it's best to use this in a home in a warmer climate that isn’t subjected to intense cold snaps.


  • Relatively energy-efficient

  • Compact

  • Quiet


  • The heating system may not be strong enough for some climates

  • Installation can be tricky

What Kind of Maintenance Does an HVAC Need?

With so many different types of HVACs to choose from, it’s not surprising that their maintenance needs vary.  

Your HVAC maintenance checklist should include an annual inspection by a qualified local HVAC service technician. Ideally, this is to check for mechanical systems to prevent issues before they occur. Technicians can also check up on control systems and electrical components to make sure everything is in good running order with your HVAC equipment. 

Many manufacturers recommend bi-yearly HVAC inspections for the best energy efficiency and to extend the life of your unit. Recommended maintenance should be performed before heating and cooling season respectively. 

Bi-yearly maintenance is especially important for any system that has separate heating and cooling components. Though there are some DIY solutions for common HVAC problems, we still recommend having a pro perform any manufacturer-recommended maintenance.

Ultimately, maintenance is key to extending the life of your unit. Most HVAC units have a life expectancy of between 10 and 25 years, but good maintenance habits can save you money long-term.

Paul Pogue contributed to this piece.

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