The **15.2 SEER2 vs 16 SEER dilemma** is an *easy* one to solve (with quite a surprising result). Namely, these new 15.2 SEER2 units are now being compared to 14 SEER, 15 SEER, and especially 16 SEER units. Let’s answer this fully by first making the distinction between SEER and SEER2 ratings:

**SEER**orrating has been in use since the 90s. It was introduced by the US Department of Energy (DOE) to express the energy efficiency of air conditioners (such as mini splits, central AC) as accurately as possible.**S**easonal**E**nergy**E**fficiency**R**atio**SEER2**orrating was introduced on the**S**easonal**E**nergy**E**fficiency**R**atio**2****1st of January 2023**as a “better” SEER rating.

Basically, the SEER2 rating is an attempt to express energy efficiency even more accurately than the SEER rating can do. There is only **1 difference** between how SEER and SEER2 ratings are measured (test conditions):

- SEER is measured at
**0.1 inches of water column**external static pressure (ESP). - SEER
**2**is measured at**0.5 inches of water column**external static pressure (ESP).

Namely, when measuring SEER2, the AC unit has to work against **5 times higher pressure** (0.1 vs 0.5 in. WC) than the AC measured at SEER test conditions. All other conditions are the same. As a result, we have come up with 13.4 SEER, 14.3 SEER2, and 15.2 SEER2 ratings.

Now, we will illustrate how these new SEER2 ratings compare to old 14 SEER, 15 SEER, and 16 SEER ratings using the 15.2 SEER2 vs 16 SEER example:

## What Is The Difference Between 15.2 SEER2 And 16 SEER AC Unit?

Due to new harsher test conditions at which we measure the SEER rating, the new SEER2 ratings are *lower* than the SEER ratings (the difference is between **4% and 5%**).

As a result, the 16 SEER unit has become the 15.2 SEER2 unit. Essentially, the **15.2 SEER2 is the same as the 16 SEER unit**.

Let’s look at an example to illustrate how the 16 SEER unit became a 15.2 SEER2 unit. Here is the equation we use to determine the SEER rating, based on the average running wattage:

**SEER Rating** = AC Tonnage Ã— 12,000 BTU Per Ton / **Average Running Wattage **

Here is what the measured and calculated SEER rating looks like:

- 3-ton
**16 SEER**AC unit has an average running wattage of**2,250W**. This was measured at 0.1 inches of water column ESP. - The same 3-ton 16 SEER AC unit at harsher 0.5 inches of water column ESP test conditions (SEER2 test conditions) had a running wattage of
**2,368W**.

We see that when we increase external static pressure 5 times, the average running wattage increases from 2,250W to 2,368W.

Now, the 16 SEER is calculated based on the 2,250W average running wattage. Under harsher SEER2 test conditions, the average running wattage increases to 2,368W. We calculate the SEER2 rating using the same SEER rating equation, but we have higher average wattage, and thus we get a SEER2 rating that differs from the 16 SEER rating.

Here is the calculation:

**SEER2 Rating** = 3-Tons Ã— 12,000 BTU Per Ton / **2,368W = 15.2 SEER2**

We can clearly see that the 15.2 SEER2 unit is just a 16 SEER unit tested under harsher test conditions. The new SEER2 rating should give us (according to the DOE) a more realistic energy efficiency metric.

In this 15.2 SEER2 vs 16 SEER case, it tells us that the 16 SEER-rated unit doesn’t run on 2,250W on average. More realistically, it runs on 2,368W average wattage, and thus we have to lower the SEER rating from 16 SEER rating to this new 15.2 SEER rating.

Nonetheless, the fact is that the 16 SEER unit is the same as the 15.2 SEER2 unit (it’s just a difference in how these ratings are measured for exactly the same mini split AC). There is absolutely no difference between 16 SEER and 15.2 SEER2 air conditioners in any way.

You can read more about SEER vs SEER2 ratings difference here.