Central Air-Conditioner and Heat Pump Efficiency 101


Couple couchMany homeowners during some point of their ownership may have to replace their central air conditioning systems. The average life span of central air conditioning system is 12- to 15- years if it is properly installed and maintained. Heat pumps have about the same life-span -- about 14 years -- when recommended maintenance is followed. Newer units manufactured in recent years are expected to last even longer.When the system starts giving you more problems than seem cost-effective to fix, it may be time to consider purchasing a new system. When faced with major repairs, consult HVAC contractors for their recommendations.

Will I need to replace my entire system?

It is important to know that split air conditioning or heat pump systems (the most common used in U.S. homes)  consist of two parts: an indoor (coil) unit and an outdoor (condensing) unit. These two parts are specifically designed to work together as a coordinated “team” to provide top performance and maximum efficiency and comfort.In the past, homeowners could sometimes replace part of their system, such as the outdoor condensing unit, to extend its useful life. However, air conditioning and heat pump systems manufactured today must have a seasonal energy efficiency ratio (SEER) of 13 or higher. 

The federal government sets the minimum efficiency standards for central air conditioners and heat pumps, which was raised to 13 SEER in 2006. For these new, high-efficiency systems to work properly and to extend their life, the outdoor unit and indoor unit must be properly matched. So if you install a new high efficiency outdoor unit, but don’t install a new, equally efficient and properly matched indoor unit, the results could be uncomfortable, unreliable, and inefficient. Because newer equipment usually is more energy efficient than older, central air conditioning or heat-pump systems, you will likely see reduced utility bills.

How can I find a contractor that performs a quality installation?  

Ask your neighbors or friends for recommendations for HVAC contractors they have worked with and trust. You should talk to a few different contractors and obtain more than one quote to compare. Another way to increase your chances of obtaining a quality installation is selecting a contractor that employ technicians who have been certified by the North American Technician Excellence (NATE).

To become NATE-certified, technicians have to pass a nationally recognized test to demonstrate they have the knowledge to properly size, install and repair today’s increasingly sophisticated heating and cooling systems. To find contractors who employ NATE-certified technicians, go to HVACR Advice and type in your zip code to pull a list of certified technicians in your area.

How can I be sure my system is the right size for my home?

Homeowners should ask their air conditioning technician to size the equipment to meet the specific needs of their homes. If a system is undersized, it will continuously run without properly cooling your home. If oversized, the system will cycle on and off too frequently, greatly reducing its ability to control humidity. It also will be less efficient.

To properly size a system for a home, trained technicians will use an equation (a “load calculation”) that factors the home’s age, the number and quality of its windows, how well it is insulated, how many stories it has, its total square footage, and other relevant factors. Homeowners should ask their technicians to perform a Manual J load calculation, the industry’s term for the standardized equation used to properly size an air conditioning system. Your technician will specify the cooling capacity of the system in either Btu/h (British thermal units of heat removed per hour) or refrigeration tons (one ton being equal to 12,000 Btu/h).

How can I determine the energy efficiency of my air conditioning or heat pump system?

Air conditioning and heat pump manufacturers are required by law to evaluate and rate their equipments energy efficiency. This standard rating for measuring central air conditioners and heat pump cooling efficiency is its Seasonal Energy Efficiency Ratio (SEER). When heat pumps are heating your home, the Heating Seasonal Performance Factor (HSPF) is used to determined its efficiency performing this function. The higher the SEER/HSPF, the more efficient the equipment.

The Energy Efficiency Ratio (EER) is also sometimes used to assess performance of residential air conditioners during hot outdoor temperatures. Many manufacturers voluntarily submit their products for testing by the Air Conditioning, Heating and Refrigeration Institute (AHRI) to assure consumers their energy efficiency claims have been verified by an independent, third party laboratory. For split systems, AHRI tests combinations of indoor and outdoor units to verify the system’s performance claims. It is important for consumers to double check the indoor and outdoor units are a certified match by asking their technician for an AHRI Certified Reference Number (formerly ARI Reference Number) or an AHRI Certificate of Product Ratings (formerly Certificate of Certified Product Performance) that can be downloaded from the CEE HVAC Directory.

How will I know if my air conditioning or heat pump system is properly matched?

You can verify your split system is a properly matched by asking your HVAC technician to provide you with an AHRI Certified Reference Number (formerly ARI Reference Number) or an AHRI Certificate of Product Ratings (formerly Certificate of Certified Product Performance). The reference number can be entered into the CEE HVAC Directory to verify that you have a matched system and to obtain a Certificate of Certified Product Performance.

For higher efficiency systems, the certificate can be used to obtain a federal tax credit or a rebate or incentive from your local utility or municipality.If you do not have an AHRI Certified Reference Number (formerly ARI Reference Number) or an AHRI Certificate of Product Ratings (formerly Certificate of Certified Product Performance) to locate your air conditioning equipment in the CEE HVAC Directory, you will need the manufacturer’s name, model name and model numbers for both the indoor and outdoor units. This information should be on the equipment’s warranty, your sales invoice and on the units themselves. Your contractor is the best source to obtain the AHRI Certified Reference Number.

How can I reduce my energy bills while maintaining comfort in my home?

Obtain a Quality Installation. Make sure your contractors installs your new equipment according to the ANSI Quality Installation Standard.

Properly seal and insulate your ducts. Sealing and insulating can reduce your total energy use by more than 20 percent. Focus first on ducts that run through unconditioned space such as your garage or attic, and seal ducts with mastic or foil-backed tape. After sealing, insulate the ducts by wrapping them in insulation.

Make sure your home has adequate insulation. A well-insulated home helps reduce the load on your HVAC system. The DOE recommends minimum insulation levels for each part of the home, based on your climate. This information can be found on the ENERGY STAR Web site.

Install a programmable thermostat. According to the Environmental Protection Agency (EPA), a programmable thermostat can save you about $150 a year in energy costs if it is properly used. It is recommended for people who are away from home during set times of the day during the week.

To increase your energy savings, the EPA recommends that you:  

  • Keep the thermostat set at energy-saving temperatures for long periods of time, such as during the day when no one is home and through the night.
  • Resist the urge to override the pre-programmed settings. Every time you do, you use more energy and may end up paying more on your energy bill.
  • Set the “hold” button at a constant energy-saving temperature when going away for the weekend or on vacation. Install your thermostat away from heating or cooling registers, appliances, lighting, doorways, skylights, and windows, and areas that receive direct sunlight or drafts. Interior walls are best.
  • If you have a heat pump, you may need a special programmable thermostat to maximize your energy savings year-round. Talk to your retailer or contractor for the details before selecting your thermostat. Maintain your system’s efficiency through proper maintenance.  Be sure to have your equipment regularly maintained. 

    Download this proper maintenance checklist for suggested practices.