How efficient should your central air conditioner be?
Let’s bust a myth right off the bat: There is no “right” efficiency for every home. There are only principles for determining what SEER level is best for your application.
Why isn’t the highest possible SEER best for everyone?
Because those central ACs are the most expensive, and the payback period in cool climates can be 12+ years.
Why isn’t the cheapest model the best for all?
Because they create the highest energy use and costs, a bad choice where the cooling season is long, hot and humid.
You get the point: There is a spectrum that runs from cheap ACs and high bills to expensive ACs and low bills.
Our goal in this AC SEER Guide is to give you correct information, so you can decide what spot on the spectrum is right for your home. We tackle common myths along the way to clear up confusion and misunderstanding.
What is SEER and AC Efficiency?
Let’s begin by defining terms.
AC Efficiency: This term refers to how much electricity your air conditioner requires to remove enough heat to cool your home to the temperature you want. The electricity is used to circulate refrigerant that captures heat inside and dumps it outside.
The more efficient the unit is, the less energy it needs to remove heat. For example, if two side-by-side homes are identical in every other way, the one with a 14 SEER AC will have cooling bills about 33% higher than the home with a 21 SEER AC. That can amount to $400 or more over the course of a warm summer.
SEER: What is that term SEER we’ve been using? If you are not familiar with the term, it’s an air conditioner’s version of gas mileage, the Seasonal Energy Efficiency Ratio. SEER is a measurement of the air conditioning output (or heat removal) the AC is capable of during a cooling season for how much electricity is used.
Cooling output over a season divided by electricity input = SEER. The higher the number is, the more efficient the AC is.
What SEER Options are Available?
In Northern states, ACs and heat pumps must be at least 13 SEER. In Southern states, 14 SEER is the minimum because the air conditioning season is longer, often from spring into fall.
Above the minimum, ACs range to as high as 26 SEER. Heat pumps range to almost 25 SEER. It seems maximum efficiency available goes up every year, so expect these top numbers to change soon.
Other Possible Benefits of High-SEER HVAC Units
For many, reducing cost along with energy use/carbon emissions are the main reasons for choosing an efficient air conditioner.
But climate control performance is also tied to SEER. It goes up as SEER rises.
- 13 to 18.5 SEER: Single-stage ACs. Most single-stage models range from 13 to 16 SEER, but the Lennox SL18XC1 changed the game with its 18.5 SEER rating. Single-stage units run at full capacity whenever on. They tend to turn on an off more often, and this creates warm/cold imbalances. Less moisture is removed, so your home will be more humid in summer. Most single-stage ACs are combined with single-stage or multispeed blowers that contribute to poor climate comfort.
- 16-20 SEER: Two-stage ACs. These units have two capacities. Low is 35% to 40% of power. High is 100% power. Running on low most of the time produces longer, gentler cooling, better temperature balance and improved humidity control. Most two-stage models are paired with variable-speed blowers that enhance indoor comfort.
- 19-26 SEER: Most units in this efficiency range have variable-capacity compressors. They modulate speed from as low as 25% depending on the brand and model to 100%. This allows the air conditioner or heat pump to run at the precise capacity needed to keep your indoor climate balanced, cool and dry.
The bottom line is that if you want improved temperature balance and dehumidification, you’ll have to buy a higher-SEER two-stage or variable-capacity system, even if you live in a cool climate and only run the AC for a couple months in summer.
The opposite isn’t true though, with the introduction of very efficient single-stage model. If you want high SEER but don’t prefer to pay extra for staged cooling, you have options like the unit like the Lennox AC (SL18XC1) mentioned above. It’s a great low-cost choice for a warm climate.
What is a Best SEER For Me?
This is where it comes down to choosing an air conditioner or heat pump with the right SEER rating for your purposes.
In our comprehensive Central Air Conditioner Buying Guide, we include a section called What Efficiency Is Right for You?
The section includes a Climate Zone map of the US divided into 7 zones. We make recommendations for SEER rating based on where you live. Generally, the warmer and more humid your climate is, the more a high-SEER unit makes sense.
We also developed a SEER Savings Calculator to help find a better balance between equipment cost and electricity cost. This tool is very customizable. Once your location is chosen, the calculator automatically inputs current energy costs and yearly cooling hours in your area. Then you will get the detailed savings comparison of different SEERs.
SEER Savings Calculator (e.g. 14 SEER vs 16 SEER)
How to Calculate the Payback Period
Determining the best SEER for your climate leads us to a discussion of a term that gets thrown around a lot. It’s a concept worth considering: Payback period.
This example explores its significance.
SEER and Equipment Cost:
AC #1 is a 14 SEER model, and it costs $1,600.
AC #2 is a 19 SEER model, so it is 36% more efficient. This AC costs $2,600, or $1,000 more. That’s about 63% more because it is also a two-stage unit.
Installation cost is the same for both models, so not a factor.
AC Operating Cost:
AC #1: Average operating costs for a 14 SEER unit are $160 for the season in a cool climate and $1,085 in a hot climate.
AC #2: Average operating costs for a 19 SEER unit are about $102 in a cool climate and $695 in a hot climate.
Comparing Payback Periods:
Cool climate: You would save $58 per year with the 19 SEER AC that costs $1,000 more. You would recoup that $1K in 17 years by cutting your AC bills $58 per year. That’s your payback period, and it’s clearly not worth it on a cost basis. Stick with the 14 SEER AC.
Hot climate: You would save $390 per year ($1085-$695) with the 19 SEER AC. The $1K higher cost would be recovered in less than 3 years. That’s your payback period, and it clearly is worth it on a cost basis. Buy the 19 SEER AC.
Ways to Keep Your HVAC Units Runing at Peak SEER
Two things will keep your AC running at its peak SEER efficiency.
First, have it installed by a reliable HVAC installer with a track record of excellence. Finding that person can be difficult, so we suggest requesting estimates from several AC and heat pump installers in your city. If you’d like to streamline the time it takes and narrow your focus on top installers, consider our Free Local Quote option. There is no cost or obligation, and the installers are pre-screened, licensed, insured and among the most experienced in your area.
Secondly, keep your AC or heat pump properly maintained. Your whole HVAC system should be checked, cleaned and tuned every few years. This maintenance will keep it running as efficiently as it should and will help prevent mechanical failure.
Other Factors in Lowering Energy Costs
There are many other factors that impact utility bills. Listed in order of importance are:
- The amount of insulation in your home: An attic that is under-insulated allows summer heat to penetrate, warming your house and causing the AC to run more than it would with adequate insulation. Read our attic insulation guide for more info.
- How well your ducts are sealed: When ducts are leaky, air conditioned air escapes from them. Some put the amount of loss as high as 30%. Cooled air escaping into the basement or attic is wasted when it’s needed in your first-floor and upstairs living areas.
- Other energy-saving improvements:House wrap, foam sealant in air gaps, triple-pane windows, weather-stripping on doors and windows and “cool roof” materials like steel or reflective shingles all contribute to lower energy use when heating or cooling your home.
Related Article: 14 SEER vs 16 SEER: Cost & Long-term Savings Comparison