AC SEER Vs Tonnage: Why Are We Still Mixing Them Together? (Explained)

SEER and tonnage are undoubtedly #1 and #2 metrics when it comes to picking an air conditioner. We found that there is quite a bit of confusion about AC tonnage vs SEER. Namely, SEER and tonnage are not connected; a 16 SEER unit doesn’t cool better than a 14 SEER unit. Here is why we see that some help is needed in understanding the connection (or lack thereof) between SEER and tonnage:

We get quite a lot of questions regarding SEER rating (in our ‘Good SEER rating’ article here) and AC tonnage (in our ‘AC tonnage calculator’ article here). There are three types of questions regarding the connection between SEER rating and AC tonnage, namely:

  1. How many tons is an AC unit with a certain SEER rating. Example of questions: “How many tons is a 16 SEER AC unit?” or “How many tons is a 14 SEER AC unit?”. This indicates that AC tonnage would be dependent on SEER rating.
  2. How many SEER for certain home sizes. Example of equations: “How many SEER for 1200 sq ft?” or “How many SEER for 2000 sq ft?”. This similarly tells us that some homeowners still think that the capacity of air conditioners depends on SEER rating.
  3. How many SEER is an AC with a certain tonnage. Example: “How many SEER is a 4-ton unit?” Again, this question clearly indicated that SEER rating and AC tonnage are somehow related.
How many tons is a 16 SEER AC unit vs 14 seer vs 20 seer
Example of three 3-ton AC units. Let’s say they have 14 SEER, 16 SEER, and 20 SEER rating. Regardless of these different SEER ratings, each of them produces 3 tons of cooling output.

Here is the deal with all of these questions:

They all indicated that SEER rating and AC tonnage should be connected. In fact, they are not; both are completely independent AC metrics. Namely, both measure different things:

  • SEER rating is a measure of the energy efficiency of AC units.
  • Tonnage is a measure of the cooling capacity of AC units.

Energy efficiency has nothing to do with cooling capacity. A 16 SEER unit can have a cooling capacity of 1 ton, 2 tons, 2.5 tons, 3 tons 3.5 tons, 4 tons, 5 tons, and so on.

Likewise, AC tonnage has nothing to do with energy efficiency. A 4-ton unit can have an energy efficiency of 14 SEER, 16 SEER, 18 SEER, 20 SEER, and so on.

Why The Distinction Between SEER And Tonnage Matters

When buying an air conditioner, we at least need to check the SEER rating and tonnage. It is important that we know what we are actually looking at when looking at a 16 SEER or 3-ton AC unit, for example.

3 ton AC unit tells us that this air conditioner can produce 3 tons of cooling output (that’s equal to 36,000 BTUs). That’s enough cooling capacity for a 1800 sq ft house, if you use simple 20 BTU per sq ft rule of thumb. A 3-ton unit will always be able to produce 3 tons of cooling output, regardless of the SEER rating.

Here are some examples to illustrate this:

  • 3 Ton 16 SEER AC will produce 3 tons of cooling output and be able to cool down a house with up to 1800 sq ft total area.
  • 3 Ton 14 SEER AC will produce 3 tons of cooling output and be able to cool down a house with up to 1800 sq ft total area.
  • 3 Ton 20 SEER AC will produce 3 tons of cooling output and be able to cool down a house with up to 1800 sq ft total area.

You see? It doesn’t matter what the SEER rating is. A 3-ton unit will always produce 3 tons of cooling output. That’s why questions like “how many SEER is a 3-ton unit” don’t really make sense.

Similar is true for the SEER rating. SEER rating only measures the Seasonal Energy Efficiency Ratio; basically, how effectively your AC unit can use the input electrical power. It tells you nothing about the size (tonnage) of the air conditioner.

Here are some examples to illustrate that tonnage is not connected with SEER:

  • 16 SEER unit has a 3-ton AC capacity. This unit will produce 3 tons of cooling output, and cool down up to 1800 sq ft homes.
  • 14 SEER unit has a 3-ton AC capacity. This unit will produce 3 tons of cooling output, and cool down up to 1800 sq ft homes.
  • 20 SEER unit has a 3-ton AC capacity. This unit will produce 3 tons of cooling output, and cool down up to 1800 sq ft homes.

As you can see, the SEER rating doesn’t change the capacity of an air conditioner. It does change, however, how much electricity your air conditioner will use.

For example:

  • A 14 SEER 3-ton unit is not all that energy efficient. It will use a lot of electricity.
  • A 16 SEER 3-ton unit has an about average energy efficiency. It will use a standard amount of electricity.
  • A 20 SEER 3-ton unit has a good energy efficiency (20 SEER is a good SEER rating). It will use less electricity to run.

You can check how the power consumption of different AC units (1-6 tons and 14-25 SEER) depends on both tonnage and SEER rating in these two articles:


Here is the correct outtake you should have about these two metrics.

Both SEER rating and AC tonnage are the most important AC metrics. They are not directly connected with one another; SEER doesn’t influence tonnage, and tonnage doesn’t influence SEER rating.

When it comes to how much it costs to run an air conditioner, however, this will depend on both SEER rating and AC tonnage. Namely, a bigger unit will consume more electricity and an AC with a higher SEER rating will consume less electricity.

Hopefully, this SEER vs tonnage dilemma makes a bit more sense now. As always, if you have any questions regarding this explanation or would like for us to help us, you can use the comments below and we will help you out.

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