SEER of 20-year Old ACs (+5 Features Your Aged AC Doesn’t Have)

Most 20 year old central air conditioners have efficiency ratings of 8 SEER to 12 SEER.

Is yours older than that? Your AC could have a SEER rating as low as 7 if it was manufactured in the early 1980s.

How Efficient Is a 20 Year Old Air Conditioner?

The SEER ratings of 20 year old air conditioners is 10 to 12 SEER. In 1992, 20 years ago, the US Department of Energy raised the minimum SEER rating to 10. There wasn’t a broad range of options – just up to 12.

And if your AC is older than 20 years, it’s efficiency could be as low as 8, going back to 1986.

New AC vs 20-Year Old AC Yearly Savings

How much can you save on your energy bill every year by upgrading an old air conditioner to a new, energy efficient unit?

The two factors are, of course:

• The SEER rating of the old unit
• The SEER rating of the new unit

This chart compares energy use and cost based on old SEER vs new SEER / lower SEER vs higher SEER.

See the notes below the chart for accurate use. Plus, we are going to recommend a cost savings calculator developed by Pick HVAC for exact savings for your system where you live.

New AC vs 20-Year Old AC Yearly Savings Comparison Chart

Your Location: If you live in very hot areas like Arizona or Texas, the savings will be higher by 50% to 100% because AC units run for many more hours per year in climates like that.

Upgraded systems: If you upgrade from a basic AC system to a two-stage/variable-speed compressor, variable speed fan or smart thermostat, the real savings will also be higher than the listed. Be sure to keep reading below for more ways to improve energy efficiency than just with a high SEER rating.

Wear and Tear = Lower Efficiency

There’s another factor you should consider – and that is that your old central air conditioner probably is not running as efficiently now as it was when new.

• If the compressor is worn, and it probably is…
• If the coils are dirty, and they probably are…
• If the unit is oversized, and it probably is because putting in ACs that were too big “just to be sure” was common until fairly recently…
• If the refrigerant is low, and it might be…

Then your old central air system is almost assuredly running below its rated efficiency.

An AC built as an 8 SEER model might be running at 5-7 SEER. A 10 SEER might give you 8 or 9 SEER.

Be Exact – Use Our SEER Savings Calculator

We’ve developed a calculator called the SEER Saving Calculator, it can be used for any AC that has a SEER rating including standard split system central air conditioners and package units.

It is simple to use – enter your data:

• System size in BTU
• SEER of the old unit
• SEER of the new unit for comparison
• Your state and the city closest to you to determine the number of yearly cooling hours based on US EPA figures

Your electric rate will appear – with data from the US Energy Information Agency

Results: The cost of running the old AC, the cost of running the new AC and the difference between them will automatically be shown.

Plus, a handy graph will be displayed using your data and showing your annual savings over 1, 5, 10 and 15 years.

The Actual SEER Rating of Your Old AC Could be Lower than the Label

Comparing SEER ratings of old/aged ACs and new ones is certainly a great way to see how much you can save on energy costs with central AC replacement.

Think about it. If you replace a 10 SEER unit from 15 years ago with a 20 SEER AC, it will cut your energy use by 50% at least – and probably more, because that old 10 SEER model might only be working at about 8 SEER due to wear, tear and aging.

Replacing an 8 SEER model with a 24 SEER AC cuts energy use by at least 67%! You can do the math for yourself by comparing SEER ratings. Divide the lower SEER rating by the higher SEER rating to see how much energy the new system will use by comparison.

For example, divide 10 by 20, and you get 50% – the new unit uses 50% of the electricity the old one used.

Divide 8 by 24, and you see the new unit uses just 33% of the power consumed by the old one when it was new.

But there are other means of getting the best possible energy efficiency from your new system. And they are explained in the next section.

5 Features Your Aged AC Doesn’t Have that Save Energy Costs

Your old AC might not have these features or components, and they boost energy efficiency.

Proper Sizing

The first feature is an AC that is the right size for your cooling needs.

In the “old days,” a lot of HVAC technicians added a half ton to a ton of AC (6,000 to 12,000 BTU of cooling) to a system just to make sure it did the job of cooling your home. Well, if you need a 3 ton system and someone installs a 4 ton AC, efficiency will be wasted. There are other problems too, like having a cool, clammy house because oversized ACs don’t remove as much humidity. And mechanical issues through short-cycling.

A 2 Stage or Variable Capacity Compressor

These units run at less than 100% power most of the time.

A two stage AC compressor runs on low capacity, which is 65%, unless a significant boost in cooling is required

A variable capacity compressor runs as low as 25% or 40% depending on the model, and rarely runs at more than 75% of capacity.

Two stage and variable capacity systems are also more efficient than single stage ACs.

The result is less energy used, just as if you could push down the gas pedal only halfway and still maintain the same speed as if you gas it all the gas.

Cost note on variable capacity ACs: They cost a lot more and are probably only worth the extra money in very hot climates like the desert Southwest and maybe in hot, muggy climates like the Southeast.

So, compare how much extra a variable capacity AC costs compared to a single stage or two stage model, and then use our calculator to determine how much you’ll save with the more efficient unit.

An Air Handler with a Variable Speed Blower

If you’re replacing the entire system, you’ll need an air handler. A furnace is a type of air handler.

A WiFi or Smart Thermostat

Most HVAC pros recommend leaving your thermostat on the same setting for optimal efficiency and comfort.

However, adjusting it slightly – a little warmer during the day while you are at work and a few degrees cooler when you are home in the evening for example – can maximize efficiency.

Learn and Save: Rather than having to remember to do that every day, a smart thermostat like nest or ecobee will quickly learn what you are doing and do it for you – adjusting the temperature at times you “trained” it to do over the course of a few days to a week or two. This makes sure the changes happen, and max efficiency is achieved.

Google says its nest thermostat can save you 15% on cooling. That’s its word; you’ll have to verify savings yourself by comparing electric costs month to month. We do believe that a smart thermostat will pay for itself in energy cost savings in a few years.

Dirty filter notification: A smart thermostat can also tell you when it is time to change the air filter. A dirty air filter can dramatically reduce efficiency and cause potential mechanical issues.

WiFi Advantage: Plus, if the smart thermostat is WiFi connected, you can make changes from anywhere. If you won’t be home on a certain evening, keep the higher temperature setting and lower it on your way home later in the evening.

Other benefits: Geofencing – your phone app sending a signal to the thermostat to switch from your Away setting to your Home setting when you get close to home – and motion sensing to boost the cooling in an occupied room and lower it when the room is empty, are other ways a smart thermostat can cut energy use and cost.

Mini Split Equipment

This is really a different type of central AC system. If you’re building a home or addition and need air conditioning, consider ductless mini splits.

We don’t have space here to break down all the differences between standard split and mini split systems, but using or not using ductwork is obviously a big one.

Two factors for mini split energy efficiency are:

Mini split compressors use inverter technology, which can be more efficient (16 to 42 SEER) compared to standard split systems (14 to 28 SEER).

Ducts can significantly reduce energy efficiency if they are leaky or if they run through hot space like an attic or garage in summer. Those issues can reduce effective SEER by several points minimum. Ductless systems don’t have those problems.

Don’t Live with Low SEER!

As you can see, there are many ways to make your HVAC system more efficient, starting with a new AC and air handler with energy efficient features. Keep it maintained. Change the filter every 3 months at least. Install a smart thermostat, and you will cut energy costs dramatically over the life of the system. 

Written by Rene Langer

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.