Understanding Efficiency: What Is A Good EER Rating for Your Air Conditioner?

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Whether you’re concerned for the global environment or your personal finances (or both), energy efficiency plays a huge role in selecting the right air conditioner. The information is often printed on the standard specification sheet for any unit, but with all of the different types of ratings, standards and labels out there, it can be hard to tell what any of it really means. 

If you aren’t in the HVAC industry, how do you know what type of efficiency rating is good for your air conditioner? What does each efficiency rating actually tell you about how the unit performs?

Understanding EER (and similar ratings) is fundamental to making a more informed buying decision for your next air conditioner. Otherwise, it may be time to invest in a new solution that saves you money or performs better in your space. In order to get the most cooling power for the least amount of energy, let’s look at how efficiency ratings work for different units. 

EER and Other Efficiency Ratings Explained

EER stands for Energy Efficiency Ratio. Used mainly for cooling devices (including PTACs), EER is a very common efficiency rating that tells you how much power (BTU) you can get out of your air conditioner for how much electricity (W) it uses. Often, it is the main specification for determining the efficiency of your AC unit. However, it’s important to know that EER is based on a single set of conditions. 

Imagine a space where the outside temperature is 95 ℉, the indoor temperature is 80 ℉, and the relative humidity is 50%. These are the conditions in which the EER rating is most accurate. 

While the true operational efficiency of the unit will depend on the specific weather and temperature conditions of the space where it is installed, the EER rating is important for comparing general efficiency across multiple units. 

Another common rating is SEER, which stands for Seasonal Energy Efficiency Ratio. This rating describes efficiency for central air conditioners and mini-splits with a range of seasonal temperatures in mind. For this reason, SEER ratings can sometimes estimate the efficiency of a unit in specific climate regions better than EER ratings. Although SEER does not apply to PTACs, some models like the Freidrich Freshaire will list an “equivalent SEER rating” for comparison.

Probably the third most common efficiency rating is CEER, which stands for Combined Energy Efficiency Ratio. CEER is specifically for window air conditioners and is mainly useful because it accounts for power consumption when the unit is in standby or idle mode. 

How to Calculate EER

Believe it or not, you can actually calculate the EER rating of any unit yourself. The formula looks like this: 

EER Rating = Capacity (Cooling BTUs) / Power (Maximum Cooling Watts)

To start, look at the specifications for an air conditioner you are interested in, and find the numbers you need to make your calculations. 

The first is the capacity measured in BTUs. BTU stands for British Thermal Unit. In literal terms, it refers to the amount of heat required to raise the temperature of one pound of water by a single degree. For our purposes, it refers to how powerful a unit is at cooling a space.  

The Maximum Cooling Watts is the amount of electrical power required to produce the most cooling effect possible (cooling BTU) for the unit. 

While the EER rating will be listed on most units anyway, seeing how these figures are used to calculate EER will help gain a better understanding of how they impact the unit’s performance. Let’s look at a few examples: 

The GREE ETAC-15HC265V30A-CP is listed at 15,000 BTU, which is a pretty high cooling capacity. The maximum cooling wattage required is 1,530 W. Let’s do the math: 

15,000 BTU / 1,530 W = 9.8

In this case, the EER rating of this model is 9.8. This isn’t a bad rating at all, but let’s look at one more example. 

The GREE ETAC2-07HP230VA-CP has only 7,000 BTU. That’s less than half the cooling capacity of the previous model. However, the maximum cooling input required for this unit is only 550 W. Here’s how to calculate the EER rating: 

7,000 BTU / 550 W = 12.7

Although the BTU for this ETAC2 is smaller, the EER rating for this unit is 12.7, which is an outstanding level of efficiency.

That’s because EER isn’t about the unit’s capacity alone. Often, people make the mistake of purchasing a larger unit for a smaller space in hopes that it won’t have to work as hard to cool the same square footage. 

In fact, the opposite is true. Oversized units can lead to moisture issues and decreased unit longevity. Instead, true efficiency is about a ratio of capacity to power. 

What is a Good EER Rating? 

Now that you know how to calculate the EER rating of any unit, you’ll be better equipped to choose a good air conditioner for your space. But what exactly is a good EER rating? 

To account for varying weather conditions, the answer usually depends on the type of unit and the space in which the unit is installed. However, you generally want to look for units that have an EER of 8.5 and above. 

Still, some regions of the United States have minimum EER requirements specifically for PTACs. You can find more details in the Department of Energy’s Energy Conservation Standards for PTACs and similar units

While early PTACs had a reputation for being inefficient, designs have drastically improved over the past decade.  Some notable models include the GE AZ65H12DAB  (EER 11.9) and AZ65H15EAC (EER 10.9), the LG LP093HDUC1 (EER 12.2), and the Midea MP09HMB82 (EER 11.4). More impressive still is the GREE E-TAC II Series. Many models in this series have equivalent SEER ratings of up to 13. 

While the most energy efficient air conditioning units are often more expensive, the upgrade is often worth it in the long run. Units with lower EER ratings can quickly drive up energy costs, especially in hotter climates. The amount you will save in utility bills will usually cover the initial cost of the unit itself in no time. 

This is also why a PTAC is a great solution for home and business owners. Even the more efficient designs can be found in some locations for less than $1,000.

How to Boost the Efficiency of Your Air Conditioner

When shopping for a new air conditioning unit, sometimes you will find the perfect match. Other times, you won’t. Choosing a more efficient air conditioner is important for a number of reasons, but you may not have the ability to make that kind of investment on a large scale just yet. 

Regardless, picking a higher number is only half the battle. How you optimize the space for the best cooling effect is often just as important as the unit’s efficiency rating. Luckily, there are a few ways you can help boost the efficiency of your air conditioner in just about any space.

Install a Programmable Thermostat

While programmable thermostats are sometimes seen as a luxury, they actually contribute to a unit’s overall efficiency. By being programmed to run only during hours when the space is occupied, the air conditioner only runs when necessary. When the space is empty, the unit can condition the space at a less comfortable temperature that requires less run time. 

Just be sure to keep any heat-emitting devices away from the thermostat so as not to throw off the sensor. This will cause the unit to run longer. 

Conduct Regular Maintenance

Maintenance is key to optimizing the efficiency and longevity of any AC unit. While some maintenance will require a technician, there are two important things you can do to make sure your unit continues to function at peak performance. 

The first is to change your air filter regularly. Not only does this improve your indoor air quality, but it also helps your unit run more efficiently. As filters collect pollutants from the air in your building, air flow through the filter is restricted. This means the air conditioner has to work harder to reach the set temperature point. To prevent this, it’s best practice to replace your air filter every three months at least. 

The second thing you should do is clean your condenser regularly. Incoming air has to pass through a condenser in order to be cooled. If the condenser is covered with dirt and debris, it will restrict air flow and make the unit run longer to achieve the same cooling effect.

Create Better Insulation

Just as a sweater keeps you warm during the winter, improved insulation can help to maintain better temperature control in any space. In many cases, this will require inspecting your existing insulation and investing in an upgrade. While you may be able to do it yourself in some situations, you might also need the help of a professional contractor.

You can further optimize your space by sealing air leaks around doors and windows with weatherstripping. By ensuring that outside air doesn’t get inside, you will keep your air-conditioned space from being inhibited by warmer air.

Final Thoughts

While there are multiple aspects to consider when selecting a new air conditioning solution, efficiency is one of the most important in any situation. From decreased carbon emissions to lower utility bills, understanding efficiency ratings can help you make a smarter choice about how you provide air conditioning for your building.

At PTAC4Less, we offer a number of new models with impressive EER ratings for residential, commercial, and industrial environments. We also have a variety of refurbished models and parts available to repair your existing units. Browse our shop or get help selecting a PTAC unit that is both cost effective and efficient.