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When It's Time to Replace
Your HVAC System

Is it time to replace my system?

The best time to replace your system is when YOU are planning on it, not when the system finally fails and you rush into a decision without careful consideration.

The useful life of a system is usually 15 to 20 years for heat pumps and 20 to 25 years for gas furnaces with air conditioners. As your system begins to wear out, you will encounter refrigerant leaks and motor failures. Sometimes, the compressor in the outdoor unit will short out or the heat exchanger in a gas furnace will develop cracks. All of these are expensive repairs and it may prove more cost effective for you to replace your system rather than repair it.

Realize Greater Efficiency and Comfort.

Today's higher efficiency systems have innovative comfort features like two stage compressors, variable speed fans, and automatic temperature/humidity controls.

These enhancements consistently convince owners to replace older, unreliable systems that have not yet completely failed. Not only will you save money on repairs, but you'll see monthly savings on your utility bills. At the same time you'll experience more consistency and comfort from your heating and cooling system system.

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What types of HVAC systems are available to choose from?

A home HVAC ("Heating, Ventilation, Air-Conditioning") system is usually composed of both a heating system and an air conditioning system. There is an outdoor unit, the "air conditioning" or "condensing" unit and an indoor unit, the air handler or furnace that contains an evaporating coil plus a blower-fan to circulate the air in your home.

In our area, heat pumps can provide both heating and cooling. But, because heat pumps cannot produce enough heat at temperatures close to freezing, they have a supplemnental source of heat fueled by electricity or gas in the indoor air handler. Air conditioners are usually coupled with gas furnaces to provide heat in the winter.

If you are replacing a complete HVAC system, you will need both an outdoor unit (heat pump or air conditioner) and an indoor unit (air handler/evaporating coil or gas funance with an evaporating coil).

In addition to the basic system you may also wish to add a humidifier or high-efficiency air cleaner to further enhance your indoor air quality.

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What factors should I consider when choosing a new system?

When you decide to replace your system, it is tempting to assume that a bigger system will solve all the problems you had with your old system. Maybe your house had hot and cold spots or your air conditioner ran all the time during the summer and you still weren't comfortable.

As the video below explains, there are a variety of solutions to indoor comfort problems. A larger system is rarely the answer to efficiency or comfort concerns. In fact, a larger system may create more problems than it solves.

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Regardless of the reason you are choosing to replace your present system, there are four factors you should consider:

1. Fuel

The types of fuel available will influence the type of equipment that can be used. Heat pumps run on electricity with supplemental heat provided by an electric resistance heater in the air handler.

If gas is available, comparative fuel costs usually indicate that an electric air conditioner coupled with a gas furnace in the most cost-efficient choice.

A heat pump can be coupled with a gas furnace. In this case, the heat pump would be used only for cooling and the gas furnace would be used for heating.

2. Efficiency

The US Department of Energy sets the standards for rating the energy efficiency of heating and cooling systems. The rating number is an indication of how much energy (electric or gas) it takes to produce one unit of heating or cooling. (See Energy Efficiency Definitions.) The terminology differs for air conditioners/heat pumps and gas furnaces.

Air Conditioners and Heat Pumps:
Efficiency in air conditioners and heat pumps is measured in terms of its SEER (Seasonal Energy Efficiency Ratio). "SEER" is similar in concept to "MPG" (Miles per Gallon)—the higher the number, the more efficiently the system uses electricity.
Since 1992, the Federal mandate for the minimum rating has been 10. Before that time, it was 8, so units that are over 14 years old are usually rated at 8 SEER.
Since January, 2008, manufacturers are no longer permitted to produce equipment that has a SEER of less than 13. With an efficiency increase of 38% coupled with higher electrical rates, it becomes easier to see why you may want to replace a system that still works with a new, higher efficiency system.
Gas Furnaces:
Gas furnaces have a similar rating system using the AFUE (Annual Fuel Utilization Efficiency) percentage. Equipment installed in the 1980's usually has a rating of 60% to 70%. Today, the minimum rating is 78% and high efficiency units have a rate of 90%. Newer equipment also has enhanced comfort and safety features not found on older furnaces.

3. Comfort

Innovations in the design of today's heating and cooling systems include features that eliminate the "heat pump chill" associated with older equipment. Two of the most significant are variable-speed blower motors and two-stage gas valves.

Variable-speed motors:
Variable-speed motors are used most commonly in the indoor air handler. They typically use less than 1/4 the electricity that the older, single-speed motors used. Their biggest comfort advantage is that they can match the air flow to changing temperature conditions.
For example, if the indoor section of your heat pump were running in the cooling mode, this motor would ramp up to its highest airflow speed for maximum comfort and efficiency.
When running in heating mode with a heat pump, the motor is typically slowed down to increase the temperature rise across the coil, thereby giving higher duct temperatures—thus, eliminating that cool, drafty feeling that people think they have to tolerate with a heat pump system.
Two-stage gas valves:
Gas furnaces have also seen improvements in comfort. It is now common to get a gas furnace with two-stage valves. This feature enables heat to be delivered to your home more evenly over time instead of heating with shorter, higher temperature bursts of heat. This allows the system to maintain a more constant temperature throughout your home.

4. Your Home's Unique Characteristics

There are many factors that affect the sizing and specifications of your system, including square footage, insulation, window surface and configuration, geographic location of your home, duct sizing and arrangement, and many others.

We can perform a Home Energy Audit to determine which equipment combinations will best suit your home and your family's needs. A Home Energy Audits will provide information to help you decide how to allocate your home improvement budget.

Most importantly—consult with your contractor early!

Environmental Systems Associates provides free, in-home evaluations to ensure that you are aware of all the choices available to you. We often find during the evaluation process that home improvements such as finished basements can make the installation of some equipment impractical. There have also been changes in building codes over the past years and the newer equipment has more stringent installation requirements.


Call us at (410) 381-7991 for your in-home evaluation.



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  • Environmental Systems Associates, Inc.
  • 9375-J Gerwig Lane, Columbia MD 21046
  • Lic. HVACR MD 01-2939