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 AC Efficiency and SEER?
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.
Size and SEER Myth: All Model Sizes of Air Conditioner Have the Same SEER Rating.
Not true. Most are like the Goodman GSXC16. It is listed as a 17 SEER AC. In reality, only the 60,000 BTU unit achieves that rating. The 24K, 36K and 48K BTU units are 16 SEER models. It’s not a major difference, but a reminder to find out the SEER rating of the size you are considering for your home.
AC SEER and Quality Myth: Higher SEER Always Means Better Quality
Efficiency is determined by the type and size of compressor and coils used and, as noted, the cooling capacity of the unit. There are high-quality central air conditioners at most levels of efficiency.
The one exception to this is that most 13 SEER and 14 SEER ACs are quite basic, certainly not among the highest-quality units from any brand. In fact, many top manufacturers have ceased making them. Their least efficient ACs are 15 or 16 SEER.
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.
Energy Cost Myth: SEER is the Only Factor in Lowering Energy Costs.
There are many other factors that impact utility bills. Listed in order of importance are:
Performance Considerations with High-SEER and Low-SEER ACs
Let’s start with a common myth.
AC SEER Myth: Lowering Energy Consumption is the Only Reason to Choose a high-SEER AC
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 mentioned above. It’s a great low-cost choice for a warm climate.
Climate Zone and Choosing an AC
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.
Climate Zone Myth: Climate Zone is the Only Consideration for What SEER to Choose.
There are times when a lower-SEER unit might be OK for a warm or hot climate: When the AC isn’t used full-time.
A 14 or 15 SEER model would be an acceptable choice in a warm climate for a vacation home, a guest apartment, workshop or other location where it is run infrequently.
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.
Moving Myth: If you’re moving soon, save money and buy the 14 SEER AC even in a warm climate because you won’t get your money’s worth from the 19 SEER AC.
While it’s true you won’t recoup the extra cost in a year or two, you might actually pay more for this decision. Why?
Smart home buyers in hot, sticky climates want to know how efficient the AC is. A 14 SEER model will turn off potential buyers with the prospect of high energy costs or having to replace the AC to bring them under control.
On the other hand, a new 19 SEER AC will help sell your home to energy-conscious, cost-conscious home buyers.
Ways to Keep your SEER Rating High
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.