Energy efficiency is an extremely important consideration when installing any type of air conditioning, such as a central AC, heat pump or ductless mini-split AC. Units that are more energy efficient will always cost less to operate, but higher-efficiency units also tend to be quite a bit more expensive. As such, you’ll typically want to try to find a balance between energy savings and initial cost when choosing which unit is best. The energy efficiency of cooling units used to be measured using a metric known as Seasonal Energy Efficiency Ratio or SEER. However, the US Department of Energy recently switched so that all new units are measured using the SEER2 scale. Here’s a look at what SEER ratings mean and the difference between SEER and SEER2.

What Is SEER and How Is It Calculated?

Air conditioning cools by removing heat from the air inside and drawing it outside, and the energy efficiency of any AC is determined by the number of BTUs of heat the system removes for every watt-hour of electricity it consumes. Calculating the energy efficiency of portable and windows air conditioners is simple as this type of unit will always remove the same number of BTUs using the same amount of electricity. This isn’t the case with central air conditioning or a ductless AC system due to the fact that the main part of the system is outside.

Fluctuations in the temperature and humidity level outside directly impact how effectively a central or ductless AC system works and how much electricity it uses. This type of system will almost always use the same amount of electricity in a set period of time, but the BTUs of heat it removes in the same time period can increase or decrease depending on how hot and humid it is outside.

As such, the only way to accurately calculate the energy efficiency of a central AC, heat pump or mini-split is to look at how many BTUs of heat it removes and how much electricity it uses over a full cooling season instead of just in one specific period of time. This is exactly what SEER does, taking an average of the energy usage and BTUs over the length of the AC season from late spring to early fall. Another way to think about SEER is as an estimate of the total yearly energy consumption.

In order to accurately calculate the SEER rating of a cooling unit, it must be tested by operating in a range of different conditions to determine how effectively it works and how quickly or slowly it cools in different temperatures and humidity levels. This test is designed to simulate the typical conditions the unit would operate in throughout the different parts of the year so as to estimate its yearly energy usage. The less energy it uses over the course of the year, the higher its SEER rating will be.

One thing you need to understand is that all AC units that are the same size will remove the same number of BTUs of heat in the same period of time. For instance, any 3-ton cooling unit will remove 36,000 BTUs per hour as every AC ton is the equivalent of 12,000 BTUs. The difference is that a higher SEER unit will remove the same amount of heat while consuming less electricity.

How Is SEER2 Different?

The US Department of Energy introduced the new SEER2 scale as a way to more accurately gauge AC energy efficiency. The SEER2 testing requirements went into effect at the beginning of 2023, meaning that all new units must now be tested and measured using this new scale. SEER2 still measures energy usage over the length of a cooling season. The only difference with SEER2 is that one of the testing parameters was slightly tweaked so that the tests more accurately simulate real-world conditions. Specifically, the static pressure in the system when testing the unit is slightly higher than it was with the original SEER scale.

Static pressure is a measurement of how much airflow resistance there is in the system. Ductless AC systems typically have no issues with high static pressure, but the static pressure is usually slightly higher than normal in the majority of central HVAC systems. This is because there are a variety of issues that can restrict how much air flows through a ducted HVAC system.

One common reason that static pressure is usually higher is that most people don’t replace their HVAC air filter often enough, which leads to the filter clogging and restricting how much air can be pulled into the system. The HVAC blower is also often dirty, which restricts how much air it can move through the system. Most homes also have at least some air leaks in the ductwork that make it harder for the blower to move air.

Why SEER and SEER2 Matter

There’s no reason to worry if you don’t fully understand how SEER and SEER2 differ or how they are calculated. Both values are listed on all new units. All you need to know is that both metrics are a way for you to easily estimate energy usage and energy savings when comparing different units.

Let’s say that you’re considering a 15 SEER (14.3 SEER2) AC or heat pump, which is the lowest-rated unit you can install in California. SEER and SEER2 allow you to quickly calculate how much lower your energy costs would be if you instead chose a higher-rated unit. As SEER increases, the energy usage decreases by just over 7% for each higher value. This means that a 16 SEER unit would lower your annual air conditioning costs by around 7% compared to if you had a 15 SEER unit. If you chose a 20 SEER unit, you’d save around 35%.

SEER can also be used to easily calculate how much a new unit will save you compared to your current unit. Let’s say that you currently have a 3.5-ton 12 SEER unit and you’re considering replacing it with a 15 SEER or 14.3 SEER2 unit. In this case, the new unit would use somewhere between 21%-25% less energy and likely save you somewhere between $100 and $150 a year. Calculating that over the average 15-year lifespan of an AC unit, you’d end up saving nearly $2,000 over the life of the new unit.

Calculating the estimated lifetime energy costs for any AC unit can also make it much easier to determine whether a much higher-rated unit is worth the added cost. In Los Angeles County, a 3-ton 20 SEER unit will typically save you between $2,000 and $2,300 over its life compared to a 3-ton 15 SEER unit. For a 5-ton 20 SEER unit, you’d usually end up saving just over $3,000 over its life. If the amount you’d save with a higher SEER unit is around the same or greater than the price difference between it and a lower SEER unit, it’s almost always best to choose the higher-rated unit since it will be more cost effective in the end.

Any time you need any new cooling unit installed, the technicians at Temp Air System Inc. can help you determine which SEER rating is best based on your budget. We carry an extensive range of ACs, heat pumps and ductless mini-splits, and we also offer professional AC repairs, maintenance and a full range of heating services for customers in La Puente and throughout L.A. County. For more information on your AC installation or replacement options, give us a call today.

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