Yes, an older air conditioning or heat pump system gets less energy efficient as it nears the end of an average lifespan. Here’s two reasons why:

1. Compressors consume more electricity and cool less efficiently after about 12 years, more or less, depending on level of use. While it is possible to replace the compressor (the main component of the outdoor unit/condenser) when it under-performs before complete failure, there is a second factor that also decreases  efficiency.
2.  Newer systems are more energy efficient in comparison to older ones, often much more. Even if your older system maintains its rated level of efficiency, a new system with the current government-mandated minimum SEER of 14 will be significantly more energy-saving than an old heat pump with a SEER of 10.

    Figuring out the percentage reduction of your electric bill for a new air conditioner is fairly simple. Subtract the SEER of your current unit from the SEER of a new system you are considering buying, and then divide that number by the SEER of the new system. For example, if you compare a 10 to a 14 SEER, the math for the savings calculation would be 14 - 10 = 4, and 4 ÷ 14 = 0.28, so the savings would 28% of the portion of the bill for home cooling. The savings when replacing a newer SEER 12 with a high-efficiency SEER 20 (like the Trane condenser shown at the top of the page) is even more: it slices a whopping 40% off your electric heating and cooling bill.

    Calculating your actual dollar savings is more complicated. If you live in Florida, like us, you use the a/c a lot more than someone in Ohio and, of course, the cost per kilowatt hour for electricity in your area also impacts your savings. We recommend using one of the online calculators, and Lennox has an excellent one at:

http://www.lennox.com/resources/energycalculator.asp

    This is not a pitch for replacing you system early, before it completely fails. Most a/c contractors in our area are always happy to tell you about the energy savings by replacing your old system instead of repairing it when it breaks down. But there is one contractor here in North Florida that proudly specializes in keeping older systems alive for 20 years and longer, and extolls the advantages of regular maintenance and holding onto them as long as possible. Also see our article How can I make my Florida air conditioner last longer?

    The next time your air conditioner or heat pump needs a major repair— between the deteriorated performance of an older system and the much higher SEER of a new one—replacing an older system before it dies is at least something to think about.

    But there are also several other factors beside age that could be reducting the performance of your system. See our blog post Why is my air conditioner not cooling enough? to learn more. 

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  To learn more about heating and air conditioning systems, see these other blog posts:

• Why does my home still feel humid and muggy with the air conditioner on?

• Why does my air conditioner keep shutting itself off?

• How can I find out the SEER of my air conditioner? 

• My air conditioner won't turn on. What's wrong? 

• How can I find out the size of my air conditioner? 

• How can I find out the age of my air conditioner or furnace?

• How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump? 

• Where is the air filter for my central air conditioner and furnace? I can’t find it? 

• How did homes stay cool in Florida before air conditioning? 

• What is wrong with an air conditioner when the air flow out of the vents is low?

• Why has the thermostat screen gone blank? 

• Why does it take so long to cool a house when an air conditioner has been off for a while?  

• What are the most common problems with wall/window air conditioners?  

• Will closing doors reduce my heating and cooling costs? 

   Visit our HEATING AND AIR CONDITIONING and ENERGY EFFICIENCY pages for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.