Comparing 16 SEER vs. 18 SEER

Energy efficiency is one of the primary considerations when shopping for an air conditioner. That’s because the less energy the air conditioner consumes, the more money you save. You may even save a few hundred over a year. Indeed, extremely efficient air conditioners can save over $1,000 within as little as five years. 

In addition to cost savings, investing in a more efficient air conditioner is an excellent way to play your part in environmental conservation. Using less electricity means the industry doesn’t have to produce excessive electricity. Remember that the process of generating electric power consumes tons of non-renewable fuels. 

So, with these considerations in mind, should you opt for a 16 SEER or 18 SEER air conditioner? Which one makes more sense financially and otherwise?

The Basics

The first step is to understand air conditioner energy efficiency ratings. Today’s air conditioners are designed to be very efficient. However, the efficiency levels vary from one AC to the next. The industry has a means for rating the appliances to help shoppers make informed decisions. 

There are three broad ways to rate AC efficiency levels;


EER is short for Energy Efficiency Ratio. It’s the ratio of the cooling capacity of an air conditioner (in British Thermal Units (BTUs)) to the power input (in watts). The higher the EER rating, the more efficient the air conditioner. 


CEER is short for Combined EER. It’s the ratio of measured cooling output (in BTU/hour) to the measured average electrical input (in watts) and standby/off-mode power consumption. Essentially, it’s a modified EER value that also considered the appliance’s power consumption on standby. The original EER value only considers power input when the appliance runs and ignores power consumption when the unit is off. 


Finally, SEER is short for Seasonal EER. It’s the ratio of AC cooling output to the appliance’s electrical input over the same period over a cooling season. So, SEER is also a variation of the EER ratio, the main difference being that SEER is measured over the entire cooling season under varying weather conditions. In contrast, EER is measured under standard climatic conditions. 

In all three cases, the higher the value, the greater the efficiency levels. Meanwhile, a lower rating denotes poor energy efficiency. 

Why’s the SEER Rating Important?

Energy efficiency ratings are important because they give buyers an indication of how much electric power you’ll likely consume. The SEER value, specifically, can be beneficial in the following three ways;

It tells you the appliance’s power consumption rate

SEER is calculated as the total cooling output over a season divided by the total electrical input over the same period. Therefore, if you know the BTU rating of your air conditioner, i.e., its size and the SEER rating, you can easily calculate the total energy consumption over a season. Then, divide the BTU rating by the SEER value. 

For instance, a 20,000 BTU air conditioner rated 20 SEER consumes 20,000/20 = 1,000 watts (1.0kw) per hour. 

It allows you to calculate the cooling costs per season

Once you’ve determined the appliance’s electric input per hour, it’s easy to calculate cooling costs. All you need to do is multiply the total power input per hour (in kilowatts (1kw = 1,000 watts)) by the cost of electricity in dollars per kilowatt-hour.

For instance, currently, electricity costs $0.1376/kwh. Thus, the 20,000 BTU AC rated 20 SEER consumes, on average, $0.1376 x 1.0kwh = $0.1376. If the unit runs eight hours daily, you will spend about $1.1/day. Assuming the average cooling season lasts 125 days or 1,000 hours, it comes to $1.1/day x 125 days = $137.6/year. 

It’s an excellent comparison point for air conditioners

Everyone wants the items. When shopping for an air conditioner, you want the most stylish, modern unit with the best features and the longest lifespan. SEER ratings allow you to compare air conditioners based on energy efficiency so that you can select the most efficient one within your budget. 

For instance, many shoppers would sooner pick a 20 SEER air conditioner over a 13 SEER unit as long as it’s within budget and meets their other needs. In addition, it promises greater energy savings and is also environmentally friendlier. 

16 SEER or 18 SEER? Which is Better?

This brings us to the original question: Which one is the better choice between a 16 SEER air conditioner and an 18 SEER unit?

Unfortunately, the answer isn’t as straightforward as you’d wish. Although the 18 SEER option appears superior at the outset, there are many other factors to consider to make the right decision. Let’s look at some of these factors. We’ll assume that you’re in the market for a standard 18,000 BTU AC. 

Energy efficiency 

 Perhaps we should start with energy efficiency. Here, an 18 SEER air conditioner wins hands down. An 18 SEER, 18,000 BTU air conditioner consumes 18,000/18 = 1,000 watts/hour = 1kw/hour. This translates to 8kw/day and 1,000 kW/year. 

Meanwhile, a 16 SEER AC consumes 18,000/16 = 1,125 watts/hour = 1.125 kW/hour. This translates to 9kw/day and 1,125kw/year. So, you’d save a lot of electricity by opting for the 18 SEER air conditioner. Over a year, you’d save 125 kilowatts. 

Running costs 

Now that we know the energy consumption rates for each option, it’s easy to determine the cost of running each AC in a day and over a heating season. Assuming the national average of $0.1376/kilowatt, the 16 SEER unit costs $0.1376/kilowatt x 9 watts/day = $1.24/day and around $154.80/year to run. Meanwhile, the 18 SEER unit costs $0.1376/kilowatt x 8 watts/day = $1.1/day and around $137.60/year. 

That’s a difference of $154.80 – $137.60 = $17.2/year in favor of the 18 SEER AC. So, here too, the 18 SEER air conditioner wins. 

Upfront costs 

This is where the tables turn and where you have to make a stand. The average cost of a 16 SEER air conditioner (including the coils) is $1,860. If you include installation costs, it comes to $3,560. Meanwhile, the average 18 SEER AC costs $2,200 (including the coils). When you add installation charges, the amount rises to $4,250. 

So, you can see that it’s a massive difference of $340 between the two – $690 if you include installation costs – in favor of the 16 SEER air conditioner. 

Time to Break Even 

From the above date, we find that it would take 340/17.2 = 19.76 months or about 20 months to break even with DIY installation and 690/17.2 = 40.11 months or about 40 months to break even with professional installation.

Given that the average mini split air conditioner has a lifespan of 14 years, with most units lasting between 12 and 16 years, you can see why choosing between a 16 SEER and 18 SEER AC isn’t very easy. Although the 18 SEER unit is more energy-efficient and less costly to run, the unit may not even live long enough to recoup the extra investment. 


Ultimately, it’s up to you. If you’d like a more energy-efficient unit and aren’t purely driven by economic concerns, then an 18 SEER AC makes more sense. However, if you’re also concerned about a return on your investment, a 16 SEER unit is more sensible. The good news is that any air conditioner above 16 SEER is considered highly efficient.