When Replacing your Old Furnace, Heat Pump, or Air Conditioner…Bigger Is Not Better

When Replacing your Old Furnace, Heat Pump, or Air Conditioner…Bigger Is Not Better

Many homeowners hope more powerful equipment will do a better job. Unfortunately, this is a common misconception. While too small is not acceptable, too big can be much, much worse. Most homeowners who buy a larger unit regret their decision. An oversized heating & cooling system leads to:

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  • Higher Utility Bills
  • More Breakdowns & Repair Bills
  • Uneven Temperatures
  • Uncomfortable Summertime Humidity
  • Increased Noise
  • Greater Duct Leakage
  • Increased Mold, Dust Mites and Allergies

If you were unhappy with your old unit, do not just assume you need a bigger one. It is rare to find a unit that actually is undersized. More often, the real problem is a weak duct system, air leaks, missing insulation, or inadequate maintenance.

Invest the time to uncover and fix the real causes of poor performance. Then, ensure your new equipment is sized correctly. Manufacturers make seven different sizes of air conditioners and furnaces for good reason. This commonsense approach will give you the most comfort, the lowest utility and repair bills, and the healthiest indoor air.

Why Equipment That is Too Powerful Is Not Better

More Breakdowns & Repair Bills. Like any mechanical device, the more often your equipment starts and stops, the more wear and tear it experiences. An oversized unit cycles on & o# excessively, causing more frequent breakdowns, higher repair costs, & a shorter life. Your new properly sized unit will be more trouble free and last longer.

Uneven Temperatures Oversizing. Forced air equipment leads to poor air distribution and uneven temperatures throughout the home. When a system short cycles, the farthest rooms simply don’t get enough cool or warm air. A correctly sized system will mix your air better, provide more uniform temperatures, and reduce hot or cold room problems.

Increased Noise & Duct Leakage. The bigger the equipment, the more air it has to move. Your existing ducts are unlikely to be able to handle the increased airflow. Oversized units operate at higher duct pressures, causing the blower motor to use more electricity. You will likely experience short, noisy, intense blasts of excessively cold or hot air. Your ducts will also leak more, wasting energy and making the house dirtier. Your right-sized unit will run quieter, be much less noticeable, help keep your air cleaner, and save money.

Problems Specific to Oversized Air Conditioners

Higher Electric Bills. An oversized air conditioner (AC) costs more to buy. It also costs much more to run over its 10-20-year lifespan. Similar to an automobile in stop & go traffic, the efficiency is reduced by excessive cycling. It takes 15 minutes for a modern high efficiency air conditioner to reach its rated performance. Oversized units often cycle off just as they have “gotten up to speed”. Homeowners with new oversized high efficiency AC equipment simply don’t get the energy savings that they paid for. A properly sized unit running for longer periods actually uses less total energy.

Higher Summertime Humidity. An air conditioner’s primary job is to cool the air. But there is more to being comfortable than that. As a side benefit an AC system also dries the air. However, an oversized AC will cool your house too quickly, and then shut o# before it has completed the slower work of removing humidity. The result: a cold clammy feeling. Many with oversized equipment and high humidity then have to over-cool their house in an attempt to be comfortable, causing much higher electric bills. Over-sizing a modern high efficiency air conditioner usually causes more humidity problems than over-sizing the older, simpler equipment.

Increased Mold, Dust Mites and Allergy Suffering. Most allergy sufferers react badly to mold spores and dust mite droppings. According to the EPA, the American Medical Association, and the American Lung Association, to ensure that mold growth and dust mites are kept at bay indoor humidity levels must be kept below 50%. An oversized AC can’t meet this standard in humid climates.


Don’t forget about those leaky ducts. A system is only as good as the duct work its connected to. To optimize your system, you may be interested in Aeroseal. Areoseal is a duct sealing product that seals your ducts and helps improve you air conditioning system in four key areas: equipment performance, energy efficiency, improved indoor air quality, and dust control. Ask us about Aeroseal!

Air Doctors Heating and Cooling, LLC are a fully licensed and insured heating and air conditioning company that serves most Southeast Michigan municipalities. Our staff is fully certified and pre-screened to provide our customers with a safe and satisfying experience. With over 100 years of combined industry experience, we take pride in solving all of your comfort needs. We are a family-based business that has been providing quality service to our neighbors for over 40 years. Contact us today to get started.