Choosing the Right HVAC System for Your Home

June 22, 2022

HVAC stands for Heating, Ventilation, and Air Conditioning.

Many homes in coastal San Diego County were built without a central air conditioning system. As summers are getting hotter, more and more homeowners are installing air conditioning.

Central air conditioning systems often cost anywhere between $5,000 – $10,000. In addition, if you have an inefficient air conditioner, you could experience high utility bills during the summer.

Before you install a new air conditioning system, here are some questions to ask:

What size HVAC system do I need?
Are there eco-friendly HVAC systems?
Does the ductwork need to be upgraded?
Are there HVAC system rebates and discounts available?

What Size HVAC System Do I Need?

Choosing the right-sized HVAC system will save you money. Too often, people are oversold on their HVAC system. As a result, they buy a larger system than they actually need. A larger HVAC system is more expensive, and can be less effective than a properly-sized system.

An oversized system often happens because HVAC installers will exchange “like for like.” That is to say, if you already have a 4-ton AC system, they will automatically sell you a new 4-ton AC system. What they forget to tell you is that the newer systems are far more efficient than the older ones. In other words, what worked in 1999 may be overkill in 2022. So, instead of automatically buying a 4-ton system, you may only need to buy a 3-ton system.

An oversized air conditioning system will blast cold air and cool your home quickly, and then shut off. Because it’s so powerful, it will continuously turn on and off. Running shorter cycles uses more energy, and can shorten the air conditioner’s lifespan. In contrast, a properly-sized HVAC system will run more continuously, which is quieter, more comfortable, and less expensive to operate.

What’s the Rule of Thumb for Sizing HVAC Systems?

Many companies agree that you should install one ton of air conditioning capacity for every 500-600 square feet. Certainly, in most cases, this is WAY TOO MUCH! One ton of air conditioning capacity may easily cool 3,000 or more square feet. Of course, every home is different.

In other words, don’t let an HVAC company choose a size based on any “rule of thumb.” If you do, you will likely buy a system that is way too large. This is why you need manual J calculations (see below).

1 Refrigeration Ton = 12,000 British Thermal Units

Air conditioners are sized by refrigeration tons. One ton equals 12,000 BTU, or British Thermal Units. A BTU is the amount of work needed to raise the temperature of one pound of water by one degree Fahrenheit. For example, one four-inch wooden kitchen match consumed completely generates approximately 1 BTU.

A 2-ton air conditioning system is 24,000 BTU. That is to say, it is rated to remove 24,000 BTUs of heat per hour.

Manual J Calculations

So how can you calculate the right size when you buy an HVAC system? Ask your contractor to use Manual J Calculations. These calculations determine how many BTUs are needed to cool your home. You can also ask an engineer to perform an Actual Load Calculation.

Are There Eco-Friendly HVAC Systems?

Some HVAC systems are more energy efficient than others. As you can imagine, this can make a huge difference on your monthly utility bill.

First, Make Your Home Energy Efficient

Are you planning on making other energy upgrades to your home? Energy upgrades, such as sealing, insulation, and new windows will improve your home’s energy efficiency. (Read more about HERS home energy assessments.) Consequently, if your home is more energy efficient, you will need a smaller system. Properly-sized systems are more comfortable, quieter, and they cost less to run.

You can also read about 7 Ways to Finance Energy Upgrades.

HERS HVAC System Testing

You or your contractor must pull a permit to install a new HVAC system. In accordance with California’s Title 24 energy codes, you will also need Home Energy Rating System (HERS) testing completed on your new HVAC system.

Every duct system needs to be tested. In addition, you may need additional tests such as airflow, fan watt draw, and refrigeration testing. Even if you don’t plan on pulling a permit, tell the contractor that you plan to. The contractor will probably do a better job if he believes that the HVAC system will have to pass these tests.

SEER = Seasonal Energy Efficiency Ratio

The measurement of energy use for air conditioning systems is called SEER. SEER measures air conditioning and heat pump cooling efficiency. This is calculated by the cooling output for a typical cooling season, divided by that season’s total electric energy input. A higher SEER number means greater energy efficiency. For example, in California, the minimum efficiency system you can buy is 14 SEER.

Every point of SEER equals approximately 8% in improved energy efficiency. As an example, a 16 SEER system will use approximately 16% less energy than a 14 SEER system.

The measurement of energy use for furnaces is the percentage of efficiency. Most furnaces have 80% efficiency. Moreover, you can choose a high efficiency furnace, which offers between 92% – 96% efficiency.

Two Ways to Make your HVAC System More Energy Efficient

Here are two important tips to maximize efficiency of your HVAC system:

Buy inexpensive air filters. The least expensive air filters are the flimsiest. This is best to maximize air flow. You’ll notice that the more expensive air filters are thicker, which slows down air flow. When you slow down air flow over the coils, they may not cool properly, and freeze. So, save your money, and choose the least expensive air filters.
Keep all the vents open. While it seems to make sense to close some vents, this actually slows down air flow. Your HVAC system was initially set up optimally at an expected air flow. Closing the vents slows this air flow, and reduces the system’s efficiency.

The Duct System Makes a Difference

Your ductwork is the delivery system for your HVAC system. Old, leaky ducts can sabotage a high-efficiency HVAC system.

Imagine spending extra money for a 16 SEER air conditioner, and a 96% efficiency furnace, only to have most of the cold or hot air leak into the attic, instead of into your home.

In older California homes, the average leakage of ductwork is 28%. Currently rules allow only 6% leakage from new duct systems. Imagine how this added efficiency can lower your utility bills!

Duct Insulation – R-value

Newer duct systems are made from a flexible, accordion-like material. It usually comes in 50′ rolls, with insulation already attached. Insulation has an R-value, which is a unit of thermal resistance. The higher the value, the more effective the insulation.

The most common value of duct insulation is R6.

Whenever you can, choose R8 insulation instead. R-8 insulation performance is worth the additional expense.

SDG&E Programs

SDG&E Financial Assistance Programs can help both homeowners and renters. You can check your eligibility for an Energy Bill Discount, and for FREE energy-efficient home improvements. Eligibility is based on your household size and yearly income. You may also qualify through household participation in certain public assistance programs.

With the California Alternate Rates for Energy (CARE) Program, you’ll receive at least 30% discount on your bill every month. In addition, you’ll receive a lower rate for your electricity use.
With the Family Electric Rate Assistance (FERA) Program, you’ll receive an 18% discount on your bill every month. FERA is for households of 3 or more.

The Bottom Line

Choosing the right HVAC system for your home can save you money in utility bills, while cutting your consumption of greenhouse gases. First, maximize your home’s energy efficiency. Then, choose a system size based on Manual J Load Calculations. Next, choose R-8 insulation for your ductwork. Finally, take advantage of SDG&E’s rebates and discounts on energy efficient HVAC systems.

A Note About Duct Cleaning – many companies sell HVAC duct cleaning service. Here’s an article explaining why it’s usually unnecessary. However, don’t confuse duct cleaning with dryer vent cleaning. For safety and efficiency reasons, have your dryer vent professionally cleaned every year.

My HVAC Story: In 2017 I purchased a new HVAC system. I was extremely pleased with the installation and the service. Firstly, owner Nathan Mundy is knowledgeable and honest . Secondly, he knows all about energy efficiency, and how to identify the best solution for your home. Finally, his prices are very reasonable. Check out California Heating and Air Conditioning at www.hvaccontractorspoway.com.

As always, contact me with any questions.

Thank you Mark Pulis for providing information for this article:

Mark M. Pulis is the owner of Residential Raters LLC, an energy efficiency firm for homes and small buildings. Mark provides consultations regarding HVAC systems, solar panel installations, energy consumption, energy efficient mortgages, and more. He is a certified Home Energy Rating System (HERS) rater by California Home Efficiency Rating Services. Mark is also certified by the Building Performance Institute (BPI) as a Building Analyst and Envelope Specialist. Contact him at (858) 869-9412 or via his website.