You can find HVAC systems anywhere from single-family homes to submarines. Any HVAC system achieves the same goal: environmental comfort. Your HVAC system creates a warm atmosphere when it’s cold outside and they cool your space in the heat of summer.

Today, we often take our HVAC system for granted – but we owe our everyday comfort to Mr. Willis Carrier. Still a household name in HVAC systems, Mr. Carrier worked as an engineer at the Buffalo (NY) Forge Company and was tasked with solving a big humidity problem in a Brooklyn publishing company that made magazine pages wrinkle. He used cooling coils to dehumidify the air by cooling water and called it an “Apparatus for Treating Air”. Eventually, he built and patented an automatic control system and formed his own company—Carrier Engineering Corporation. The first well-designed cooling system was designed for theaters in Los Angeles in 1922 and quickly made its way into homes and businesses across the country.

The first well-designed cooling system from 1922.

What is an HVAC System?

HVAC stands for heating, ventilation, and air conditioning. The system brings fresh air from outdoors, heats or cools it to a comfortable temperature and distributes it throughout the house using a series of ducts. In addition to heating and cooling, HVAC systems provide better quality of air indoors by removing moisture, smoke, odors, heat, dust, airborne bacteria, carbon dioxide, and other gases from the air as it is filtered and circulated.

Types of Heating and Cooling Systems

The three main functions of any HVAC system are interrelated, but they all work slightly differently. Your heating and air conditioning system is often one of the most complicated and extensive systems in your home, so it’s worth understanding the five main HVAC systems.

1. Heating and Cooling Split Systems – The most common type of HVAC system is a split system. This system is split between two main units, a furnace, and an air conditioner. The furnace is usually located in the basement of the home while the air conditioner lives outside. Air is dispersed by either a fan or evaporator, to circulate throughout the space. This system uses a traditional thermostat to manage the temperature and is packaged with purifiers and humidifiers so no matter what the weather is outside, your home is comfortable inside. A split system can be used in extreme heat or extremely cold areas without any restriction.

Heating and cooling split systems.2. Hybrid Split System – A hybrid system employs an electric heating system, which sets it apart from traditional split systems. They can switch between gas power, which is quicker and more complete, to electric, which is more efficient and quieter. This is more useful in mild climates where the homeowner can decide how much to heat their home and keep the electric bills low. The rest of the system is essentially the same as a traditional split system.

Hybrid split systems switch between gas and electric.

3. Duct Free (Mini-Split) – A duct-free, or mini-split system, is a unique system with individual HVAC units in each room. A duct-free system is great for homes built without ductwork and provides greater independent control room-by-room. This installation process is expensive, but a great option for new additions to homes, garages, attics, or service businesses like hotels or venues.

Duct free systems are in each individual room.

4. Packaged Heating and Air – This system is a compact heating and air unit, both stored within the house so it’s useful for smaller spaces or smaller houses. These types of HVAC systems are very efficient, and easy to maintain but generally used only in warmer climates since they don’t generate very strong heat.

Packaged heating and air systems are easy to maintain.

5. Heat Pump – A heat pump is like a heat transporter that moves warm air from one place to another depending on the season. Even in cold air, a heat pump can move the heat energy that is present and transfers it inside. When it’s warm outside, it reverses directions and acts like an air conditioner to remove hot air from your home. These systems are best for moderate climates.

How a heat pump works in the different seasons.

Common HVAC Problems

Ideally, your HVAC system will work perfectly smooth with a fresh filter and the occasional cleaning. However, many small problems can turn into big issues if they aren’t serviced early.

1. Lack of Maintenance – This is the number one cause of serious problems. Regularly scheduled maintenance by a licensed service contractor is necessary to keep your system in proper working order. Without it, you’ll most likely experience unexpected costly breakdowns, increased energy cost, poor performance and frustration.

2. Dirty Filters – Homeowners should replace their filters regularly. This extends the life and efficiency of your furnace. If your filter is dirty, it will restrict airflow and cause your unit to work much harder than necessary.

Dirty filters are a common HVAC problem.

3. Blown Fuses or Tripped Breakers – Anytime your blower must work overtime due to a dirty filter, blocked airflow, or duct leaks, it can cause a tripped breaker and more energy consumption.

4. Unusual Noises – A whining or squealing motor is not normal. This is usually a sign that an inducer motor or blower motor is failing. Other noises may be caused by airflow issues or dirty burners. Either way, ignoring noises will likely only make them worse.

5. Pilot or Ignition Problems – Any type of pilot light or ignition problem should be handled by a trained service technician. Common pilot or ignition problems include a dirty pilot, flame sensor, or burner issues that cause pilot outage, short cycling, furnace lockout, or delayed ignition of the burners.

6. Running Blower – If the blower on your fan is running continuously, there’s likely an issue. It could be a setting on the thermostat, or a circuit board issue on the furnace. A trained service technician can evaluate this problem and offer repair options.

7. Mechanical Wear and Tear – There are several mechanical components like belts and bearings your system relies on. These components require oiling and cleaning and will wear out over time.

8. Thermostat Problems – Frequently, when your HVAC is not working properly, it’s not a HVAC issue at all. It’s a problem with the thermostat. Programmable thermostats may have batteries which need to be replaced periodically.

9. Dirty Coils – A dirty evaporator coil reduces the efficiency of both your furnace and air conditioner and makes your system work harder.

10. Water Leaks – Both air conditioners and furnaces produce condensate. If you notice a water leak, a technician should be called to check the collector box, heat exchanger or evaporator drain.

Water leaks are a common HVAC problem.

Signs of a Replacement

Your HVAC system represents a significant investment. It’s important to take care of your system and keep it running as long as possible. But how do you know when it’s time for a replacement? There are a few clear signs that it’s time to consider replacing your system:

  • It is near the end of its average life expectancy – The Department of Energy recommends homeowners replace their HVAC system every 10 to 15 years. While today’s AC units are durable, the major components will begin to deteriorate over time and with heavy use.
  • A repair cost is more than half the price of a new system – If your AC is out and you’re wondering whether to repair or replace it, it mostly comes down to numbers. If your repair will cost 50% or more of the new system cost, AND it’s upward 10 years old, it’s time to replace it.

Repair versus cost of replacement.

  • Your energy bill keeps increasing, but your rate remains the same – Your utility bills will fluctuate during the year, but if you notice your bills are increasing consistently, it could be a problem. This is usually because your system is starting to deteriorate and is working harder to maintain the same temperature, causing an increase in utility bills.
  • You have trouble keeping your home at a comfortable temperature – Even if you keep your thermostat the same, you may start to notice your air conditioning is having a harder time keeping up. This is a sign that it is no longer powerful enough to get the job done and it may be time to replace it.
  • Reduce Air Quality – Part of the responsibility of an AC system is to provide proper ventilation throughout the home. If you notice more dust, dander, dirt, mold, mildew or humidity, your AC isn’t doing its job.
  • Weird smells – Any time you notice an odor from your ventilation system, you want to hire an HVAC contractor as soon as possible to check it out. This can be a serious situation, or it could be nothing more than built-up dust burning off. Either way, weird smells are a sure indicator that something isn’t right.
  • Odd sounds like grinding or squealing – Most HVAC systems are quiet. You may hear a fan turn on, but nothing more than that and certainly not any grinding, screeching or banging. Any unusual sounds are a sure sign that your system needs attention ASAP.

Benefits of Replacing an Old HVAC Unit

Replacing your HVAC system can be one of the greatest changes for your home. Replacing old units is safer, easier, and often cheaper than running an old system.

  • Saves You Money – A new HVAC system is an investment in your home that will save you money in utility costs every single month.
  • More comfort – Today’s HVAC systems can provide more even temperatures throughout your home than older systems. You can precisely adjust temperatures for rooms throughout your home, times of day, days of the week, etc.

Having a comfortable home is a benefit of a well working HVAC system.

  • Reduced noise – Newer HVAC systems are almost silent. They have high-tech sound absorbing materials to keep their motor and running noises to a minimum. No more turning up the TV every time the AC fan kicks on.
  • Better Efficiency – New high-efficiency HVAC systems use about a third less fuel as compared to older models. So, not only are you saving money in the long run, but you are also reducing your carbon footprint and producing less waste.
  • Wider variety of add-ons – Thermostats have come a long way in recent years. Today, you can program the thermostat to remain at a temperature that limits energy consumption while you’re at work. Then turn it on while you’re sitting in traffic. You can shut it off while on vacation and have the house comfortable by the time you land. All you must do is pull out your smartphone to adjust anytime, anywhere.
  • Higher resale value – If you are planning to sell your home anytime soon, it’s worth replacing your system. You’ll be able to recoup part of the costs in resale, and chances are your buyers will ask you to replace it anyway.
  • Tax credit – In some areas, you can get a serious tax credit for disposing of old, inefficient systems and replacing them with high-efficiency options. This is worth looking into to see if you can get paid to install a new HVAC.
  • More extended warranties – With today’s units, you don’t have to worry about it going out next year and replacing it again. Most manufacturers will offer extended warranties that give you peace of mind moving forward.

How Much Does a New HVAC System Cost?

The average cost to replace your HVAC system is $7,000 with a typical range of $5,000 to $10,000. The exact cost can fluctuate based on several factors:

  • Size – Bigger is more expensive, not necessarily better. You want to choose the correct size based on your square footage and climate.
  • Quality – The best HVAC brands will last 18-25 years and usually come with a more comprehensive warranty.
  • Performance – Typically, you will pay a little bit more for a higher SEER score. A SEER score of 13-15 is the lowest performing whereas scores of 20-24 are the top performers.Look for the SEER rating on new units.
  • Efficiency – Efficiency is measured in BTUs and is usually determined by the climate you live in. If you live in a hotter climate, you need a system with a higher BTU (22-30).

What Size HVAC System Do I Need?

When choosing an HVAC system, you want to make sure to get one that is just the right size.

Get one too small, and it will be in constant overload. Get one too big and you are wasting money. The size you need is based on BTUs. A BTU is the energy required to raise 1 pound of water 1-degree Fahrenheit.

There are several ways to calculate the number of BTUs your home requires. These calculations use the square footage, climate in your area, ductwork specifications, insulation, etc. There are complicated calculators you can use online – but the best way to get an accurate estimate is to have a professional HVAC contractor size your space.

Generally speaking, hotter climates need 18 – 30 BTUs per sq. foot while cooler climates need 12 – 20 BTUs per sq. foot. For a specific size recommendation, you’ll need an HVAC contractor in your area.Each climate zone may require having a certain size unit.

Maintenance Tips for Your HVAC

Keeping your HVAC investment in tip-top shape is essential for maximum comfort all year long while keeping your energy bills low.

  • Keep the outdoor unit clean and clear of dirt and debris.
  • Use a programmable thermostat to help your HVAC work efficiently, especially when you’re not home.
  • Keep up on annual maintenance.
  • Change the blower filter at least twice a year, more often if you live in a dusty area.
  • Insulate and air-seal your home properly.
  • Maintain smoke and carbon monoxide alarms


In general, most HVAC systems will last from 15 to 25 years depending on the type of system and the quality of maintenance.

HVAC refers to heating, ventilation, and air conditioning, whereas AC simply refers to air conditioning. HVAC includes air conditioning, but AC doesn’t include heating or ventilation.

The outdoor unit should be in a shady area away from vegetation and clean of debris. The indoor unit should be as close to the center of the home as possible, in a closet or room that is insulated and relatively easy to access.

In a perfect situation, an air conditioner should run for 15-20 minutes at a time in mild temperatures. It will run slightly more on especially hot days. If your AC is running shorter than that, it’s likely too big for your home.

There are some covers available for outdoor HVAC units, but they aren’t usually necessary. Putting any type of cover over your air conditioning unit can trap moisture and cause mildew or mold on your outdoor unit. They are designed to withstand weather, so it’s best to leave them alone.

Making Comfort a Priority

Americans spend over $11 billion per year on the monthly costs to heat and cool their homes. That represents a significant investment in keeping your home and family comfortable throughout the year. Your HVAC system protects your home and everything inside from moisture, heat exposure, and frigid temperatures. Understanding your HVAC system and how to care for it can extend the life of your unit, save you on monthly costs, and keep you comfortable all year long.