Energy costs are skyrocketing, inflation is higher than it has been in years, and there is a call for more energy-efficient buildings to help fight climate change. You may be looking at that old AC and wondering if it is worth replacing with a more energy-efficient model. If this is you then you are probably also wondering “is a higher SEER rating worth it?”
The higher the SEER rating the more energy-efficient the AC. For the best price per performance, homeowners should choose a SEER rating between 16-20.
What is a SEER rating?
First, let’s define SEER ratings and how they are calculated.
SEER stands for Seasonal Energy Efficiency Ratio. It is the most popular metric used to describe the energy efficiency of an air conditioner. The other two are Energy Efficiency Ratio (EER) and Coefficient of Performance (COP). We will get to these in a later post.
Let’s say you put a watt meter on your air conditioner. Then you monitor how much electricity (in watt-hours) is used over an entire cooling season. Furthermore, let’s also assume that you were able to measure how many BTU of cooling were produced over the same cooling season.
If you were to divide the amount of cooling produced by the amount of electricity used you would get the SEER rating.
SEER = (cooling output in BTU over a season)/(electrical energy input in Wh during the same season)
Therefore, the higher the SEER rating the less electricity used to produce the same amount of cooling. This gives us a very handy tool to easily compare the efficiency of different AC units.
What is the minimum SEER rating allowed?
Before we can discuss the higher efficiency air conditioners it is useful to have a baseline. Did you know that the US Department of Energy (DOE) imposes minimum efficiency standards for all appliances, including air conditioners?
The minimum SEER ratings also differ by geographical location.
North: 13 SEER
Southeast: 14 SEER
Southwest: 14 SEER (and EER restrictions)
Please note: The DOE is changing the testing regulations for SEER to be more stringent. On January 1st, 2023 the minimum SEER rating will effectively increase by 1 point for all regions.
Is there a big difference between 13 SEER and 16 SEER?
Now that we have a baseline for our air conditioners we can finally start to compare SEER ratings. Since SEER is a ratio we can very easily compare two units simply by dividing them. For example:
Is there a big difference between 13 SEER and 16 SEER?
Grab out your trusty calculator and divide 13 SEER by 16 SEER. The number you get is 0.8125. That means that the 16 SEER air conditioner should be 18.75% more energy-efficient than its 13 SEER counterpart. For every $100 of electricity that the 13 SEER unit consumes the 16 SEER unit will save you $18.75.
That’s a lot of savings!
The formula for comparing two SEER ratings is:
Savings percentage = [1-(Smaller SEER)/(Larger SEER)] ×(100)
We can now compare each AC matchup and see exactly how much energy we will save with the better AC.
Is a higher SEER rating worth the cost?
We now have half of the information to answer this question. If we only had the yearly cost to run the AC we could make a decision!
Let’s do it!
I live in Colorado where my electricity costs roughly $0.13/kWh. According to ASHRAE, my AC will run 716 hours a year. I also have a 3 ton Air Conditioner.
For more information on AC sizing read: The Reason Air Conditioners are Measured in Tons.
On average it costs me $258 a year to run my 13 SEER air conditioner. A 16 SEER air conditioner would cost me $209 to run, a $49 savings.
That may not sound like a large amount of money. However, consider that the lifespan of an air conditioner is between 10-15 years. The savings over 10 years would be $483. The savings over 15 years would be $725.
The cost difference between a 13 SEER and a 16 SEER model is roughly $250. Therefore, the 16 SEER air conditioner is the better choice over the lifetime of the unit.
We can do the same calculation for different SEER ratings, and I suggest that you do so. What I have found is that the 16-20 SEER air conditioners generally give you positive savings over the lifetime of the unit. However, as the equipment gets more energy-efficient it gets more costly. You start straying into a marginal rate of return issue.
The cost of the units grows exponentially with the SEER rating. The incremental cost of the unit starts to outweigh the cost savings at around 20 SEER.
However, it is impossible to factor in the rising price of electricity. You will always see a higher return on your investment over time as energy costs increase.
Does a higher SEER cool better?
More energy-efficient air conditioners naturally cost more. There may be an expectation for these units to also create higher levels of comfort in your home. Is it the case that higher SEER ACs cool better?
In general, no.
Remember that air conditioners have nominal sizes. A 3 ton AC will have a cooling capacity of roughly 36,000 Btu no matter if it is 13 SEER or 21 SEER.
Side note, if you haven’t read The Reason Air Conditioners are Measured in Tons yet, now is a fantastic time!
Again, SEER is a ratio of the cooling output per energy input. Since the size of the unit is the same the cooling output will be roughly the same. Therefore, the only change will be to amount of electricity used to power the unit.
Furthermore, since the cooling capacity is roughly the same the temperature of the air coming out of your duct work will be the same. Therefore, there should be no change in comfort for the same sized air conditioner. Regardless of SEER rating.
What is a two-stage AC?
There is one exception. There is such a thing as a 2-stage air conditioner. You start to run into them around the 16-17 SEER range. This equipment is built with a high stage and a low stage. The high stage will be the rated capacity (let’s say 3 Tons). However, the low stage will be lower (let’s say 1.5 tons).
In other words, the air conditioner can ramp itself down to produce less cooling. You may be wondering why you would want such a feature.
LESS COOLING? My system already struggles to keep up!
The reason is that on moderate days it takes less cooling to get your house down to a comfortable temperature. You only need the high stage on the hottest days. We call these design days.
Furthermore, using high stage on moderate days can cause short cycling (where your system turns itself on and off quickly) and poor comfort. Short cycling also means less humidity control. The system isn’t running long enough to pull moisture out of the air. This can cause the humidity in your home to increase which can also cause comfort issues.
If you live in a humid area then it may be worth investing in the two-stage air conditioners to help maintain comfortable relative humidity levels. If you don’t live in a humid area but have issues with short cycling you may also want to look into a two-stage unit.
Operating on low stage also saves you money as it takes less electricity to cool your home.
Want to learn more about comfort in dry and humid climates? Check out Wet Bulb Temperature vs. Dry Bulb Temperature. Trust me, it’s worth the read!
So which SEER rating should you get?
The answer is simple. If your goal is to make your home as energy efficient as possible then get the highest SEER rating you can afford.
You also probably want a two-stage or variable speed compressor. I’m personally a fan of the ducted mini-split units. They are quiet, super high-efficiency heat pump units. I have had good luck with both Daikin and Hitachi.
If your goal is to make the best financial decision then I would get a unit with a SEER rating between 16 and 20.
The energy savings will more than pay you back for the cost increase over a 13 SEER unit. A nice 16 or 18 SEER, two-stage unit is probably the sweet spot. I have had great luck with Goodman/Amana units in this range.
Either way make sure that you keep the area around your condenser free, clean them off yearly, and have a certified professional service them once a year. Air conditioners are expensive, and maintaining them properly will help them last longer.