What Does HVAC Stand For? Breaking Down the Acronym

Published onNovember 21, 2024
Energy and Environmental, Resources

HVAC stands for Heating (H), Ventilation (V), and Air Conditioning (AC). Together, these elements make up the complete HVAC system, each playing a role in delivering year-round comfort and air quality.

Table of Contents

What is the Purpose of a Heating, Ventilation, and Air Conditioning System?

An HVAC system’s primary goal is to create a comfortable and healthy indoor environment, regardless of the weather outside. It does this by:

Heating (H) to Keep Your Home Warm

Heating is one of the main functions of an HVAC system, responsible for keeping you comfortable indoors when outside temperatures drop.

The heating component in an HVAC system might include a furnace, heat pump, or boiler. These run on different fuel sources, such as electricity (heat pumps), natural gas, propane, or oil (furnaces and boilers).

The type of heating system used usually depends on the local climate, the fuel options available, and the homeowner’s energy efficiency preferences.

Let’s take a look at these different heating systems:

Furnaces

Furnaces heat the air by burning fuel—usually natural gas, propane, or oil. A combustion process creates heat, which is transferred to the air that moves through the furnace.

Fans then blow this heated air through ducts and vents to raise the temperature in each room.

Image credit: Blue Water Climate Control

Boilers

Boilers work differently. Instead of heating air, they heat water.

Using fuel sources like natural gas or oil, a boiler heats water, which is then circulated through a network of pipes connected to radiators or underfloor heating systems.

The warm water (or steam) heats the surrounding air, providing steady, even warmth without blowing air around.

Image credit: Holtzople

Heat Pumps

Heat pumps extract heat from outdoor air (even in cold weather) and move it indoors.

Unlike a furnace or boiler, a heat pump doesn’t create heat but instead transfers it, making it very efficient, especially in moderate climates.

The heat pump uses refrigerant to pull heat from the outside air, then compresses it and releases it indoors to warm your home.

Ventilation (V) for Fresh Air Circulation

Ventilation is necessary for maintaining indoor air quality. It brings in fresh air and removes carbon dioxide, dust, allergens, and pollutants.

A good ventilation system keeps indoor air fresh and comfortable. It also helps control oxygen and humidity levels, preventing excess moisture and maintaining a comfortable dew point in the living area.

This is especially important in newer, energy-efficient homes that are tightly sealed, where air can quickly become stale without proper ventilation.

Ventilation systems often include filters that capture dust, allergens, and other pollutants, improving the air quality and making it healthier to breathe.

In homes with advanced HVAC systems, air exchangers bring in fresh outdoor air while removing indoor air, maintaining a consistent flow of fresh air without wasting energy.

Air Conditioning (AC) for a Comfortable Indoor Temperature

AC, or Air Conditioning, is the cooling component of an HVAC system.

It works by removing heat from indoor air and cooling it before being circulated back into the home to lower the temperature and minimize humidity levels.

The key player in the cooling process is refrigerant. This special fluid flows through the evaporator coil inside your home, where it absorbs heat from the indoor air.

As it absorbs heat, the refrigerant changes from a liquid to a gas, carrying the heat with it.

The refrigerant—now in gas form—moves to the compressor in the outdoor unit.

The compressor increases the pressure and temperature of the refrigerant, preparing it to release the stored heat effectively.

In the outdoor coil, the refrigerant cools and condenses back into a liquid as it releases the absorbed heat into the outdoor air.

The cycle then starts again as the cooled refrigerant flows back to the indoor unit to absorb more heat.

Image credit: Energy.gov

Humidity Control to Balance Moisture Levels Indoors

Humidity control is another component of an HVAC system. It balances moisture to prevent the air from becoming too dry or humid.

A humidifier adds moisture during dry winter months, while a dehumidifier reduces excessive moisture in the summer. Controlling indoor humidity improves comfort and helps prevent mold from growing.

HVAC Terms and What They Mean

When you’re shopping for an HVAC system, there are a few key terms and acronyms you’ll see a lot.

These explain how the HVAC system performs, how energy efficient it is, and which features add comfort and convenience.

Knowing these terms ahead of time can help you better understand what each model offers and will make it easier to compare the different options—from their individual heating and cooling capacities to their efficiency ratings.

Here are some of the most important HVAC terms you should know:

BTUs (British Thermal Units)

BTUs measure the amount of heating or cooling an HVAC system can provide. The BTU rating is one of the most important numbers to consider when choosing an HVAC system.

For heating, BTUs indicate how much heat the system can add to the air in an hour, while for cooling, BTUs measure the system’s capacity to remove heat.

If the BTU level is too low, the system may struggle to reach or maintain your desired temperature, working harder and potentially leading to higher energy costs and a shorter lifespan.

However, if the BTU level is too high, the system may short cycle—frequently turning on and off—which can lead to uneven temperatures and wasted energy.

Manual J HVAC Load Calculation

You can find a lot of charts online that’ll tell you the BTU load needed based on your home size, but these calculations are too simplistic and aren’t going to always be accurate.

They’re just multiplying the square footage by a fixed number, which only gives you a general idea.

For a more precise calculation, the Manual J formula is recommended. This method considers several important factors, including:

The climate you live in.
The total square feet of living space.
The height of your ceiling.
How many windows and exterior doors you have.
How many people live in the home.
Insulation quality.
Your desired indoor temperatures when heating and cooling.

These variables are all taken into account to give you the heating and cooling BTU loads needed for your home.

To make the entire calculation easier for you, use our HVAC load calculator to determine your exact heating and cooling BTUs needs.

Built on industry-standard Manual J principles, our calculator will give you BTU and tonnage estimates tailored to your home’s unique requirements.

Tonnage

A “ton” refers to the cooling capacity of an air conditioning system, not its weight. Historically, this measurement originates from the amount of heat required to melt one ton (2,000 pounds) of ice over a 24-hour period, which equates to 12,000 British Thermal Units (BTUs) per hour. This means a 1-ton air conditioner can remove 12,000 BTUs of heat per hour from your home.

To figure out the size of the air conditioning unit you need in tons, you can take your home’s cooling requirement in BTUs from the calculation above and divide that number by 12,000.

For example, if your home requires 48,000 BTUs for cooling, you would need a 4-ton unit (48,000 / 12,000 = 4 tons).

SEER (Seasonal Energy Efficiency Ratio) Rating

SEER ratings measure how efficiently an air conditioner or heat pump cools your home over an entire cooling season. It’s calculated by dividing the total cooling output (in BTUs) by the energy consumed (in watt-hours) during that time.

A higher SEER rating means the system uses less energy to cool your home, which translates to lower electricity bills. For example, a unit with a SEER rating of 26 is among the most energy-efficient options available.

SEER ratings are especially important for people living in regions with long, hot summers. In these areas, cooling systems run frequently, so a system that can provide season-long efficiency makes a big difference.

SEER2

In 2023, the Department of Energy updated the SEER rating system to SEER2, setting new minimum efficiency standards based on the region and type of unit.

Minimum SEER2 Standards by Region

Region	Air Conditioners	Heat Pumps
Northern States	13.4 SEER2	14.3 SEER2
Southern States (<45,000 BTU)	14.3 SEER2	14.3 SEER2
Southern States (≥45,000 BTU)	13.8 SEER2	14.3 SEER2

To qualify for Energy Star certification, systems that use air conditioners or heat pumps must have a minimum SEER2 rating of 15.2.

EER2 (Energy Efficiency Ratio)

Unlike SEER2, which measures the cooling efficiency over an entire season, EER focuses on how well a cooling system performs at one constant outdoor temperature.

It shows the ratio of the cooling output (in BTUs per hour) to the electrical energy input (in watts). It’s calculated under a set of standard conditions:

Outdoor temperature: 95°F
Indoor temperature: 80°F
Relative humidity: 50%

A higher EER means better performance during peak heat.

The EER rating of a cooling system is especially helpful for commercial units that run nonstop in hot conditions.

For homeowners who live in consistently hot climates, paying attention to the EER rating is essential. It helps them predict energy costs and determine if a system can handle the heat in their area without costing too much.

EER2 Ratings and Efficiency Levels

EER2 Rating	Efficiency Level
11 and above	Excellent efficiency
9.5 to 10.5	Very good efficiency
8.5 to 9.4	Good efficiency
8.4 ane below	Poor efficiency

AFUE and HSPF: Heating Efficiency Ratings You Should Know

AFUE (Annual Fuel Utilization Efficiency) and HSPF (Heating Seasonal Performance Factor) indicate the efficiency of heating systems:

AFUE (Annual Fuel Utilization Efficiency)

AFUE is the efficiency rating for furnaces and boilers. It measures how much fuel is converted into usable heat versus the amount wasted.

Higher AFUE ratings mean better fuel efficiency, which can significantly reduce heating costs.

For example, a furnace with an AFUE of 90% turns 90% of its fuel into heat, while 10% is lost. This rating is especially relevant for systems using natural gas, propane, or oil.

AFUE Ratings

Standard Efficiency: 80% to 85% AFUE

Older furnaces and some standard models typically fall in this range, meaning they convert 80-85% of fuel into heat, with the remainder lost as exhaust.

High Efficiency: 90% to 98.5% AFUE

High-efficiency furnaces (especially condensing furnaces) can reach 90% efficiency or higher. Top models can achieve up to 98.5% AFUE, wasting very little fuel.

HSPF (Heating Seasonal Performance Factor)

HSPF applies to heat pumps and measures their efficiency in heating mode.

It’s calculated by dividing the total heating output (in BTUs) over a season by the total electricity used (in watt-hours).

For example, an HSPF rating of 10 means the system provides 10 BTUs of heat for each watt-hour of electricity consumed, indicating strong energy efficiency.

HSPF Ratings

Standard Efficiency: 7.7 to 8.5 HSPF. This range is common for standard heat pumps, which provide adequate efficiency but may have higher operating costs in very cold climates.

High Efficiency: 8.5 to 10 HSPF and above. High-efficiency heat pumps have HSPF ratings of 8.5 or higher, with some models reaching up to 13. Systems in this range don’t consume as much electricity, making heating more cost-effective.

Heat pump systems with higher HSPF ratings are better for homeowners who live in moderate climates, where the heat pump does most of the work.

HSPF2

HSPF2 is a new rating standard introduced in 2023 to measure heat pump efficiency more accurately in real-world situations.

It improves on the older HSPF rating by using stricter testing methods that reflect updated efficiency standards and how people use heat pumps today.

HSPF2 ratings are usually lower than HSPF ratings for the same unit. This is because the new tests provide a clearer view of how much energy the units actually consume.

Here are the main differences in HSPF2 testing:

Fan Power Usage: It looks at how much energy fans use during heating cycles, which can lower efficiency ratings slightly.
Modern Seasonal Load Profiles: It considers how homes are insulated, how thermostats are used, and heating needs in different regions today.
Wider Temperature Range: It tests performance in colder weather, where heat pumps work harder and may be less efficient.
Higher Static Pressure: It simulates issues from duct resistance caused by long duct runs, bends, or partially blocked vents.
Ductwork and Air Leaks: It includes inefficiencies that often happen in real duct systems.

HSPF2 Ratings

Standard Efficiency: Heat pumps with an HSPF2 rating between 6.8 and 7.5 provide enough efficiency for basic heating needs. However, they may lead to higher energy costs, especially in colder areas.
High Efficiency: Units with an HSPF2 rating of 7.5 or higher are very efficient. They produce more heat while using less electricity, which helps lower energy bills and reduce carbon footprints.

HSPF2 gives a clearer picture of a heat pump’s performance in everyday use, helping homeowners make better decisions when comparing different models.

Take Advantage of Tax Credits for Energy-Efficient HVAC Systems

Investing in a high-efficiency HVAC system with high AFUE or HSPF ratings not only lowers your heating costs but may also qualify you for federal tax credits.

These credits can help offset the upfront cost of more energy-efficient heating systems.

You can learn more about federal tax credits for HVAC systems by visiting ENERGY STAR’s Home Savings page.

Single-Stage vs. Multi-Stage and Variable Speed Systems

The “stage” of an HVAC system refers to its operating speed:

Single-Stage Systems

Single-stage HVAC systems operate in a single, full-power setting. This means they’re either completely on or off. They’ll run until the thermostat reaches the set temperature and then shut off.

While simple and affordable, single-stage systems struggle to provide consistent comfort and can lead to higher energy costs in extreme climates.

Multi-Stage Systems

Multi-stage systems offer more flexibility by operating at two or more power levels depending on temperature needs.

They’re able to give more precise temperature control, usually operate quietly, and are more energy-efficient than single-stage systems since they don’t always run at full power.

For example, they’ll run at a lower setting on mild days where it’s easy to maintain indoor temperatures and shift to higher power on days that are either really hot or cold

The most common are two-stage systems with low and high settings, but three-stage and even five-stage systems exist.

Variable Speed Technology

Variable speed technology takes multi-stage operation a step further.

With this feature, the blower motor continuously adjusts its speed based on the heating or cooling needs of your home. Instead of switching between fixed stages, it adjusts automatically.

This means the system only uses the energy it needs at any moment, which saves more energy.

Also, variable speed technology reduces temperature changes and keeps air circulating continuously. This helps filter out dust and allergens more effectively.

Smart HVAC Systems

Smart HVAC systems can connect to Wi-Fi and be controlled remotely through a smartphone app. These systems offer advanced features that help optimize comfort and energy usage:

Advanced Control: You can adjust settings from anywhere, which is useful for turning the system on or off when you’re away from home.
Energy Tracking and Reporting: Some smart HVAC systems monitor your energy usage and will give you insights into how you can reduce your costs.

Smart Home Integration

Many smart HVAC systems are compatible with other smart home devices, allowing you to control your HVAC system using voice commands or integrating it with other smart features in your home.

The Different Types of HVAC Systems and How They Work

Choosing the right type of HVAC system depends on your home’s needs, layout, and climate. Each system offers unique advantages, whether you’re looking for customized comfort, energy efficiency, or a space-saving design.

Here’s a breakdown of the main types of HVAC systems available.

Split Systems

A split system is one of the most common types of central HVAC systems, named for its design, which “splits” the system into two main components: an outdoor unit and an indoor unit.

These components work together to heat or cool your home by circulating air through a network of ducts, giving your home full temperature control in every room. Additional components, like the compressor, expansion valve, and refrigerant lines, work together to regulate temperatures.

While split systems cover the whole home, they do require significant space for ductwork, which can be a challenge in older or smaller homes.

Different Types of Split Systems

1. Air Source Heat Pump Systems

Air source heat pumps are a type of split system that handles both heating and cooling in one unit. Rather than generating heat, these systems transfer it:

In Summer: The heat pump functions like an air conditioner, pulling heat from your home and releasing it outside.
In Winter: The heat pump reverses the process, drawing warmth from the outdoor air (even in cold weather) and bringing it indoors.

While highly efficient in moderate climates, heat pumps may struggle in regions with extended periods of very cold weather.

To address this, most air handlers used with heat pumps come with backup electric resistance heat strips that will kick in when it’s too cold outside for the heat pump to extract enough warmth to maintain the desired indoor temperature.

While these heat strips help maintain comfort in extreme cold, they use a lot more energy than when the heat pump is able to transfer heat itself, leading to higher energy bills when used often.

For this reason, heat pumps are often paired with a more efficient backup heating source, like a gas furnace in colder climates. This is what’s known as a dual-fuel or hybrid system.

2. Dual Fuel Systems (Hybrid Split Systems)

Dual fuel systems combine a heat pump with a backup furnace, typically powered by natural gas, propane, or oil.

These systems automatically switch between the heat pump and furnace based on outdoor temperatures to keep your system running efficiently and your home comfortable.

Mild Weather or above freezing: The heat pump provides the heating using electricity.
Cold Weather or below freezing: The furnace takes over when temperatures drop too low for the heat pump to operate efficiently.

You can also set the temperature for when you want your system to switch energy sources which gives you a way to optimize the efficiency.

This smooth transition between energy sources keeps your heating system running at its best while delivering extra comfort when you need it most without relying on heat strips.

3. Ductless Mini-Split Systems

Ductless mini-split systems are essentially a type of heat pump, designed to provide both heating and cooling in a compact, flexible package.

They’re an excellent option for homes without existing ductwork, new additions, or smaller spaces like garages and basements.

These systems allow homeowners to set different temperatures in individual rooms or zones, providing a customized and energy-efficient experience.

Like traditional heat pumps, mini-split systems use a refrigeration cycle to transfer heat rather than generate it.

Each system includes an outdoor unit connected to one or more indoor units through a small conduit. This conduit holds the power cable, refrigerant tubing, suction tubing, and condensate drain.

Because mini-splits don’t rely on ductwork, there’s less energy loss typically associated with central forced-air systems. This can make them a more efficient option, especially in homes where adding ductwork isn’t practical.

The indoor units can be mounted on the ceiling or wall, and installation is relatively simple, requiring only a small hole (about 3 inches in diameter) in the wall for the conduit.

Many mini-split systems also use variable speed inverters, which adjust the compressor speed to match your heating or cooling needs. This technology helps save energy, keeps indoor temperatures consistent, and reduces operating costs over time.

4. Geothermal Heat Pump Systems

Geothermal systems use the earth’s natural underground temperature to heat and cool your home. These systems consist of three main components:

A ground loop (a network of pipes buried underground)
A heat pump
A distribution system to distribute air like ductwork or radiant floors.

They work by circulating a fluid through the ground loop to transfer heat between your home and the ground.

In the winter, the ground loop absorbs heat from the earth as the fluid circulates through the pipes. This heat is transferred to a heat exchanger in the heat pump, where it’s concentrated and distributed throughout a home.

In the summer, the system removes heat from your home and releases it back into the ground, cooling the living space.

The ground loop is the most important part of a geothermal system, and its design depends on the available space on the property and the soil conditions.

Horizontal Ground Loops: These are installed in shallow trenches, typically 4–6 feet deep. They require a significant amount of land, often covering up to 1/4 to 1/2 an acre for a typical residential system. This option is best for homes with plenty of open yard space and less rocky soil for easier excavation.
Vertical Ground Loops: For properties with limited space, vertical loops are a the alternative. These are installed by drilling boreholes 100 to 400 feet deep, depending on how large the system is. These are more expensive to install but take up much less space, which is helpful on smaller lots.

Many geothermal systems include a component called a desuperheater, which uses waste heat from the heat pump to heat water.

This feature is especially useful in the summer when the heat removed from your home can be repurposed to provide free hot water. During winter, the desuperheater reduces the cost of heating water by using heat sourced from the ground—cutting water heating expenses by up to 50%.

While geothermal systems are highly efficient and eco-friendly, it can cost a lot to have them installed because of the excavation or drilling required for the ground loop.

However, for homeowners looking for sustainable long-term energy solutions, geothermal systems can save them a lot on heating, cooling, and hot water.

Packaged Systems

In a packaged system, all heating and cooling components are combined into a single outdoor unit. They’re typically installed on a concrete pad directly next to a residential home or on rooftops for commercial buildings.

Since everything is outside, these systems are typically used when there isn’t enough room to install a separate furnace or air handler in the home or when a homeowner is just looking to save indoor space.

Packaged systems come in both all-electric and gas pack models (which use gas for heating), giving homeowners flexibility in choosing the best fuel option for their heating needs and preferences.

Image credit: Goodman

Variable Refrigerant Flow (VRF) or Variable Refrigerant Volume (VRV) Systems

VRF (Variable Refrigerant Flow) and VRV (Variable Refrigerant Volume) systems are advanced HVAC options mainly used in commercial buildings, but they’re becoming popular in large homes.

These systems connect multiple indoor units to a single outdoor unit, allowing for independent temperature control in each room or space.

One of their main advantages is flexibility.

VRF/VRV systems can adjust the amount of refrigerant sent to each indoor unit, precisely heating or cooling specific areas as needed—minimizing energy waste and lowering energy bills.

They can even heat one space while cooling another at the same time if needed.

If you’ve got a big home and like the idea of dialing in the perfect temp for every room, VRF/VRV systems are definitely worth considering.

What to Expect During a Home HVAC System Installation

Getting a new HVAC system installed is a big project. But if you know what to expect, it can make the whole process go more smoothly.

From prepping your space to the final testing and maintenance tips, here’s an high-level overview of what happens during a typical HVAC replacement.

Preparing Your Home for Installation

Before installation day, you’ll need to prepare your home to make sure the technicians have clear access to all areas where they’ll be working.

This includes clearing space around the furnace, air conditioner, or any other existing HVAC equipment, as well as any attic or basement areas if needed.

You should also plan for some noise and foot traffic while they remove the old equipment and install your new system.

The Initial Walkthrough

Once the installation team arrives, they’ll do a walk-through. This is when they’ll check your current system, measure your space, and confirm everything matches the plan.

They’ll also be on the lookout for any unexpected issues—like ductwork that needs to be repaired or if your electrical system needs to be upgraded.

Removing the Old System

Next comes the teardown. The installers will remove the old HVAC unit, ductwork (if needed), and other related components. Again, this part will get a bit noisy but it’s usually pretty quick.

Installing the New System: What the Technicians Do

Once the old equipment is removed, the technicians will install the new system and connect all the necessary components.

For central systems, this might involve installing ductwork, an air handler, and a condenser unit, while ductless systems require mounting individual indoor units in each zone.

The process includes wiring, refrigerant charging, and making sure all the parts are correctly connected for efficient operation.

Technicians will set everything up properly and should be following local codes and safety standards.

System Testing and Calibration

After installation, the HVAC technicians will test the entire system to make sure it’s working like it should. They’ll measure airflow, make sure the thermostat is working and accurate, and calibrate the equipment to match your home’s specifications.

How Long Does it Take to Have an HVAC Unit Installed?

Most installations are completed within a day. However, if it’s a bigger job that involves adding new ductwork or installing a multi-zone system, it can take two or three days.

Your technician will give you a more specific timeline based on your particular installation and it should be on the quote they give you for the job so you’ll know what to expect ahead of time.

The Importance of Regular HVAC System Maintenance After Installation

Once your new system is installed, your HVAC technician should walk you through basic maintenance tasks to keep it running smoothly. This includes things like:

Changing Filters: Replace air filters every 1–3 months to maintain airflow, reduce strain on the system, and improve air quality by trapping dust and allergens.
Cleaning Vents: Regularly clean vents and return vents to remove any dust that’s built up so your home and system get enough airflow.

This is basic care that’ll keep your new unit running efficiently and prevent unexpected breakdowns.

Many technicians will also recommend signing up for annual maintenance to keep the system running efficiently over time. Professional maintenance typically includes:

1. Duct Cleaning

Over time, dust and debris can build up in your ductwork, reducing system efficiency and spreading allergens. Having your ducts cleaned restores optimal airflow and improves indoor air quality.

2. Tune-Ups

During a seasonal tune-up, the technician inspects critical components like the compressor, evaporator coil, and refrigerant levels. They also check and clean the heating elements when needed. This maintenance helps find small problems before they become expensive issues.

3. Thermostat Calibration

They’ll check your thermostat to make sure it’s properly calibrated for accurate temperature control. This is one of the easiest ways to prevent energy waste.

Regular maintenance of your HVAC system will keep it running efficiently year-round, extend its lifespan, and minimize the risk of expensive repairs.

A little effort in maintaining your HVAC system goes a long way toward reliable comfort and keeping your energy bills in check.