As energy costs and environmental concerns grow, selecting efficient HVAC systems can make a significant difference. People today want lower energy bills and effective cooling in all weather conditions. This is where energy efficiency ratings come in handy. If you are in the market for a new HVAC system, then you will encounter two common ratings in the form of EER (Energy Efficiency Ratio) and SEER (Seasonal Energy Efficiency Ratio). EER and SEER ratings give essential insights into how air conditioners use energy under specific conditions.
But without the knowledge of EER and SEER, it can be challenging to make a buying decision. In this guide, we will make a EER vs. SEER comparison guide and understand how you can use these energy ratings to save on energy expenses as well as minimize your carbon footprint.
NOTE: There are new ratings in town; SEER2 and EER2. As this is a basic guide, we want to cover the original quantities. We already made a SEER vs. SEER2 comparison guide. Check it out for more information on newer energy efficiency ratings.
What is EER?
Energy Efficiency Ratio or simply EER is a measure of an air conditioning system’s efficiency under specific conditions. We can use this metric to understand how well an air conditioner performs at a fixed, high temperature. EER measures the cooling output of an air conditioner in British Thermal Units (BTU) per hour and compares it to the power the unit consumes in watts.
The formula for calculating EER is:
EER = Cooling Capacity (BTU) / Power Input (Watts)
For example, if an air conditioner provides 12,000 BTUs of cooling power and consumes 1,200 watts of electricity, its EER would equal 10 (12,000 BTU / 1,200 watts = 10 EER). A higher EER indicates a more efficient unit, as it delivers more cooling power per watt of energy used.
How is the EER Calculated?
Manufacturers calculate EER under pre-determined and fixed testing conditions. The process occurs in a standardized environment with the outdoor temperature set at 95°F, indoor temperature at 80°F, and indoor humidity at 50%. These conditions are similar to typical hot summer days in many regions.
During testing, the manufacturer measures the cooling capacity in BTUs that the air conditioner produces in one hour. At the same time, they track the exact number of watts the unit consumes.
Since EER only accounts for performance at one temperature, it does not adapt to fluctuating conditions. This limitation means EER functions as a straightforward, fixed metric that provides insights into performance during peak heat but offers less information about seasonal or varying temperature efficiencies.
When EER is Most Relevant?
EER ratings are most helpful in hot climates where temperatures remain high and consistent over time. In these environments, EER can indicate how efficiently a unit will cool a space when outdoor temperatures climb, as they tend to do in places like Arizona, Texas, and Southern California.
People living in regions with steady summer temperatures can benefit from high-EER air conditioning units because these systems reduce electricity costs during peak cooling times.
EER’s focus on single-temperature efficiency makes it less applicable for areas where temperatures vary widely across the day or season. For instance, residents of cities with moderate climates, such as San Francisco or Seattle, may find EER less relevant, as their air conditioning systems rarely face sustained high temperatures.
Typical EER Values
EER values vary depending on the type of air conditioning unit and its intended use. For room air conditioners, EER values usually fall between 8 and 12. Higher EER values within this range indicate better efficiency. AC units rated 10 or above are generally energy-efficient for single-room cooling.
For larger central air conditioning systems, EER ratings often range from 11 to 14, although premium models can achieve EER values as high as 16 or 17.
A “good” EER rating typically depends on the cooling needs and climate of the user. In regions with intense heat, an EER rating of 12 or higher maybe a worthwhile investment due to its potential energy savings.
Keep in mind that models with higher EER ratings often cost more upfront. However, their efficient operation can offset these costs over time by lowering electricity bills.
What is SEER?
The Seasonal Energy Efficiency Ratio, or SEER, is a measure of how efficiently an air conditioning system operates over a typical cooling season. Unlike other ratings (EER), SEER accounts for the reality that outdoor temperatures change throughout the year.
This rating paints a more realistic picture of efficiency across a range of temperatures as it considers an AC system’s ability to handle fluctuations in demand.
The formula for SEER is straightforward: SEER equals the total cooling output over a cooling season divided by the total energy input over the same period.
SEER = Total Cooling Output (BTUs) / Total Energy Input (Watt-hours)
A higher SEER rating indicates better energy efficiency i.e., the system uses less electricity to produce the same amount of cooling. SEER provides a valuable tool for comparing the energy efficiency of different systems.
How is SEER Calculated?
To calculate SEER, manufacturers perform a series of controlled tests at multiple temperatures to mimic real-world conditions. During testing, SEER calculations take place across a range of temperatures. This is typically in the range of 65°F to 104°F as it represents the variety of conditions an air conditioner will face in a typical cooling season.
Lower temperatures represent cooler days with light cooling needs, while higher temperatures represent hot days with peak demand. Testing across a range of temperatures makes SEER a comprehensive measure for areas with varying weather patterns.
When SEER is Most Relevant?
SEER ratings are very valuable in regions with variable temperatures or moderate climates where the cooling season includes both warm and hot days. In these areas, air conditioners frequently operate at different intensities.
SEER rating is useful for homeowners in places with mild-to-hot weather since it provides a realistic view of a unit’s energy demands.
In climates with consistently higher temperatures, SEER is still helpful, but it may not account for extremes. For example, if the temperature frequently stays above 100°F, SEER ratings become a less precise indicator of efficiency. In these cases, EER (Energy Efficiency Ratio), which measures efficiency at a fixed temperature, is a better indicator.
However, SEER is highly informative for most regions with fluctuating or mild temperatures.
Typical SEER Values
SEER ratings typically range from 13 to over 20, with higher numbers indicating greater efficiency. The U.S. Department of Energy (DOE) sets minimum SEER standards, which vary by region. The DOE mandates a minimum SEER of 14 in northern states and 15 in southern states.
Warmer regions demand higher SEER ratings because these areas require more cooling, making efficiency more important.
While a SEER of 13 or 14 meets minimum standards, systems with SEER ratings of 16 or higher are often a better investment (in the longer run).
EER vs. SEER – Comparison Table
To clarify the distinctions between EER and SEER, the table below provides a side-by-side comparison of several key aspects:
| Feature | EER | SEER |
| Temperature Consistency | Measures efficiency at a constant outside temperature | Considers seasonal temperature fluctuations |
| Use Case | Ideal for stable climate conditions | Best for areas with varying seasonal temperatures |
| Impact of Climate | Less influenced by climate variations | Significantly affected by climate changes |
| Understanding Efficiency | Focused on maximum potential efficiency | Focused on average, long-term efficiency |
| Units of Measurement | Calculated at specific conditions (BTUs/watt) | Calculated over a range of conditions (BTUs/watt-hour) |
| Impact on Performance | Consistent performance under fixed conditions | Variable performance, optimal for seasonal use |
| Cost Implications | Lower upfront cost, and higher operational costs in fluctuating climates | Higher upfront cost, lower operational costs |
| Market Use | Common in commercial and industrial sectors | Predominantly used in residential settings |
| Energy Standards | Varied standards based on region and application | Often driven by national energy efficiency programs |
EER vs. SEER: Key Differences
1. Temperature Conditions and Testing Standards
EER ratings measure an AC unit’s efficiency at a single, fixed temperature, typically 95°F. This rating is determined by testing the air conditioning unit under controlled conditions, where outside temperatures, humidity, and other variables are constant. An AC with a high EER might seem very efficient, but its performance can drop significantly when outdoor temperatures fluctuate.
In contrast, SEER ratings represent an AC unit’s efficiency across a range of temperatures, from 65°F to 104°F. SEER calculations assess the unit’s performance over an entire cooling season rather than at a single fixed temperature.
This range gives SEER a broader perspective on energy use i.e., how the system adjusts to temperature changes throughout the season. SEER thus provides a more realistic, dynamic, and seasonally adjusted data.
2. Applicability to Different Climates
The most significant distinction between EER and SEER is in their relevance to different climate types. EER has significant advantages in hot, arid, and stable climates where high temperatures and humidity remain relatively constant.
In most southern states of the U.S, where summer temperatures consistently exceed 90°F, EER’s single-temperature efficiency measure gives a straightforward estimate of energy use. It is ideal for window air conditioners or cooling devices in regions with minimal temperature changes. Businesses like data centers and laboratories, which need precise climate control, rely on EER ratings to ensure efficiency under steady conditions.
SEER, however, becomes more valuable in regions with varying seasonal temperatures. In areas like the Midwest or Northeast United States, temperatures can range widely over the course of a cooling season. SEER’s seasonal approach of testing captures these variations and shows how efficiently a unit can perform.
For these regions, SEER is a more practical indicator of energy efficiency, since it averages the unit’s performance over an entire season. A high SEER rating means the air conditioner remains efficient despite climate fluctuations, offering effective cooling and energy savings.
3. Units of Measurement
EER, or Energy Efficiency Ratio, is found by dividing the cooling capacity in BTUs per hour by the power input in watts. It measures how effectively an air conditioner converts electricity into cooling under fixed conditions. This makes EER useful in stable environments where temperature and humidity don’t change much.
SEER, or Seasonal Energy Efficiency Ratio, measures total cooling output in BTUs over a cooling season divided by the total electrical input in watt-hours. SEER includes various temperatures, giving a broader view of efficiency in changing weather. This makes SEER more relevant for residential systems in variable climates.
Frequently Asked Questions:
SEER is generally more important as it reflects real-world performance. However, EER can be helpful in hot climates where the AC runs constantly at higher outdoor temperatures.
Higher EER and SEER ratings indicate a more efficient air conditioner. This translates to lower energy consumption and electricity bills.
Not necessarily. Higher SEER units often come with a higher initial cost. Consider your climate, budget, and how long you plan to stay in your home.
The potential savings depend on your current system’s efficiency, local energy costs, and AC usage. However, high-SEER units can significantly reduce energy consumption and electricity bills.
How To Choose Between Them: EER vs. SEER?
When choosing between EER and SEER for an air conditioner, understand their differences. EER measures efficiency at a constant temperature, ideal for stable environments like commercial settings. SEER, on the other hand, measures efficiency over a season, suitable for residential use with varying temperatures.
EER is best if your area has stable temperatures, while SEER is better for regions with seasonal changes. A higher SEER rating means better energy savings and comfort during hot periods.
Consider your location, climate, and usage when deciding. EER is beneficial for minimal temperature fluctuation, while SEER suits areas with significant seasonal changes. Choosing the right rating impacts your comfort, energy consumption, and costs, making it a wise investment in your financial and environmental future.
Thank you for reading through the comparison of EER vs SEER. We hope this guide has helped clarify the differences and will assist you in making an informed choice about the best air conditioning system for your needs.
If you need more details or have any specific questions, feel free to reach out or leave a comment below!
