HVAC stands for Heating, Ventilation, and Air Conditioning.

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

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?
  • What about my ducts?
  • What HVAC system rebates and discounts are 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. 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.

This often happens because HVAC installers will exchange “like for like” – if you already have a 4-ton AC system, they will sell you a new 4-ton AC system. What they don’t tell you is that the newer systems are far more efficient than the older ones. Instead of automatically buying a 4-ton system, you may only need to buy a 3-ton system.

An over-sized HVAC system will blast cold air and cool your home faster, and then shut off. It will continuously turn on and off. Running shorter cycles uses more energy, and can shorten an air conditioner’s lifespan. In contrast, a properly-sized HVAC system will run continuously, which is quieter, more comfortable, and less expensive to operate.

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. This is WAY TOO MUCH! One ton of air conditioning capacity may easily cool 3,000 or more square feet. Every home is different.

Don’t let an HVAC company choose a size based on any “rule of thumb,” or you will likely buy a system way too large. This is why you need manual J calculations (see below). Here’s a great article from Energy Vanguard explaining why rules of thumb don’t work.

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. One four-inch wooden kitchen match consumed completely generates approximately 1 BTU.

A 2-ton air conditioning system is 24,000 BTU. 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. 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.) If your home is more energy efficient, you should need a smaller system to condition your home. 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.  You may even 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, knowing 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. In California, the minimum efficiency system you can buy is 14 SEER.

Every point of SEER equals approximately 8% in improved energy efficiency. For 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. You can choose a high efficiency furnace, 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:

  1. 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.
  2. 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, leaking 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 the air it produces leak out of the ducts into the attic, instead of into the rooms your want to heat and cool.

In older California homes, the average leakage of ductwork is 28%. A new duct system is only allowed a 6% leakage rate. 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.

HVAC System Rebates and Discounts

AC Quality Care

Get a rebate of up to $1,250 toward a new air-conditioning system through SDG&E’s AC Quality Care. This service is designed to increase indoor comfort, air quality and energy efficiency.

Through the Quality Maintenance rebate program, SDG&E customers with an HVAC system are eligible to receive a $50 System Assessment & Improvement ($300 value). You can also qualify for rebates for advanced services and upgrades.

A qualifying contractor will thoroughly inspect your system and equipment. This includes checking airflow, fan, motors, furnace, condenser and evaporator coils, compressor, air filter, and electrical components. The contractor will also change the air filter and clean the condenser coil. You will receive a detailed report showing any additional maintenance or repairs, and the rebates available to offset the costs.

More SDG&E Programs

Shop for Stand-Alone Air Conditioners

The SDG&E Marketplace has a list of energy-saving stand-alone air conditioners.  They don’t qualify for rebates, but they will save you money in energy costs.

Free Water and Energy Savings Kit

A complimentary Water and Energy Savings Kit includes a hand-held, low-flow showerhead, three faucet aerators, and an LED sensor night light.

Financial Assistance

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 or by your household participation in certain public assistance programs.

  • With the California Alternate Rates for Energy (CARE) Program you’ll receive at least a 30% discount on your bill every month. You’ll also receive a lower rate for your electricity use.
  • With the Family Electric Rate Assistance (FERA) Program you’ll receive a 12% 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. Choose R-8 insulation for your ductwork. Finally, take advantage of SDG&E’s rebates and discounts on energy efficient HVAC systems.

UPDATE: I recently installed a new HVAC system, and was extremely pleased with the installation and the service. Owner Nathan Mundy is knowledgeable and honest – he knows all about energy efficiency, and how to identify the best solution for your home. Check out California Heating and Air Conditioning at www.hvaccontractorspoway.com.

Good luck, and as always, contact me with any questions.

Thank you Mark Pulis for providing information for this article:

Mark PulisMark 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. He 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.
Mylene Merlo is a licensed REALTOR® with Allison James Estates & Homes in Carlsbad, California. As a Carlsbad Real Estate Agent, I specialize in residential North County San Diego real estate. I have earned the Green designation and the Short Sales and Foreclosure Resource certification from the National Association of REALTORS®. If you have any questions about real estate in Carlsbad, Cardiff-by-the-Sea, Encinitas, Escondido, Oceanside, San Marcos, Solana Beach, or Vista, call or text me at (760) 637-7231 or send me a message.

One thought on “Choosing the Right HVAC System for Your Home

  1. I really like that you say to find the right sized HVAC unit to help you save. Until recently, I thought that a bigger system would actually help you out. It would be nice to find a unit that is just right for my house, and won’t break the bank.

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