Have you ever noticed the SEER and EER numbers on air conditioners in a store and wondered why they’re there? SEER stands for Seasonal Energy Efficiency Ratio, while EER stands for Energy Efficiency Ratio. Before purchasing an air conditioner of any type, it’s important to understand what SEER and EER ratings are, how they’re calculated, and why it matters when it comes to choosing the right system. 

Similarities and Differences Between SEER and EER Ratings

EER ratings are a standard measurement of how fast a room is cooled based on an outdoor temperature of 95 F. It rates an air conditioner’s energy efficiency when the outdoor temperature is at or extremely close to 95 F. The higher the number, the more efficient it is. It’s an overall efficiency rating, which is handy to use when comparing different types of air conditioners. If you’re trying to decide between a ductless mini-split, portable, or window unit, EER helps you understand the efficiency of each.

SEER measures how much heat is removed from a room and takes seasonal variables into consideration. It’s unlikely that temperatures will be at 95 F all day and night, every day of the week. SEER ratings are therefore calculating the air conditioner’s efficiency at a variety of outdoor temperatures ranging from 65 F to 104F. As it covers fluctuations, it’s one of the best ways to measure a central AC unit’s efficiency over an entire season rather than just in specific situations. Again, the higher the number, the better.

How EER and SEER Are Calculated

Before you can begin to understand how companies calculate EER or SEER, you need to understand the term BTU or “British Thermal Unit.” This is a measurement of how well a unit is able to cool or heat your home. A BTU is the amount of energy needed to increase the temperature of a pound of water by one degree Fahrenheit. The higher the BTU, the bigger a space an air conditioner can cool. A smaller room like a bedroom would need less BTU than a whole house.

You also need to understand wattage. A watt is a unit of power that all appliances use. It’s the rate of how fast the energy is moving. One watt equals one joule per second. To understand what a joule is, you need to understand a newton. A newton is the amount of force needed to move one kilogram a meter per second, every second. A joule measures the force needed to move a newton one meter. Less wattage means less electricity is needed. Higher wattage means more electricity is used.

Now that you understand BTU and wattage, you can get to the formula used to calculate EER. It’s simply the BTU divided by the wattage. If you have a portable room air conditioner that’s 10,000 BTU and 1,000 watts, the EER is 10 (10000/10). 

That’s how EER is calculated. SEER looks at different loads and runs the calculations on that.

You run the unit at 100% for 1% of the time, 75% for 42% of the time, 50% for 45% of the time, and 25% for 12% of the time. To figure this out, take your EER ratings and do the math.

• 1 x 100% of EER
• 42 x 75% of EER
• 45 x 50% of EER
• 12 x 25% of EER

Once you have those add them together and divide by 100 to get SEER ratings. It’s complex and that’s why it’s easier to read labels and brochures to get the EER and SEER ratings. Remember higher is better.

The U.S. Energy Information Administration sets minimum ENERGY STAR standards for SEER ratings. For states in the Southeast, central AC SEER ratings should not be lower than 13. This is going to increase to 15 in 2023. EER ENERGY STAR standards depend on the size of the AC unit.

• Systems under 65,000 BTU – 12.0 EER (single package) or 12.5 EER (split system)
• Systems 65,000 to 134,999 BTU – 12.2 EER
• Systems 135 to 239,999 BTU – 12.2 EER
• Systems 240,000 to 759,999 BTU – 10 EER
• Systems 760,000 BTU or higher – 9.5 EER

If a system is both heating and cooling, the EERs change slightly.

Take a Closer Look at Different Models and Their Ratings

SEER ratings are often used to measure efficiency in central air conditioning units because they run for entire seasons. With a window AC, you only run it when you need it and put it away in the winter. 

Daikin is one of several companies that make air conditioner units. Their basic models have a SEER rating of up to 18 or less, but if you want an energy-efficient model, Daikin has systems with SEER ratings of up to 24.5. Goodman also offers energy-efficient models with SEER levels of up to 24.5.

What other brands have high SEER levels? Rheem and Ruud both have models with efficiencies of up to 20.5. Trane has an ENERGY STAR model with a SEER of up to 22. Finally, York has models with up to 21 SEER.

Which brand is right for you? It’s hard to know without talking to a specialist. Your home’s insulation values, exposure to the sun, ceiling heights, and square footage all impact your choice.

Bigger is not always better. If an air conditioning system is bigger than you need, it will turn on and off frequently, which wears the compressor and fan controls. As it’s turning on and off too quickly, not every room stays as cool as it should. A room with a thermostat may be cool enough, but bedrooms are warmer, making for uncomfortable sleeping.

 If it is too small, it has to run continuously to try to keep the room cold, which can cause your electricity bills to skyrocket. It also strains the components in the AC system as they’re running all of the time. It can overheat or build up ice on the evaporator coils, causing the system to shut down unexpectedly. Once it shuts down, your home heats up until it’s able to turn back on. Once it does, it works harder to get the rooms cool again. It’s going to wear out and need replacement before you expected to replace your AC system.

Ask About a Unit’s ENERGY STAR Rating

There’s an easy way to get the most efficient central AC unit possible. Talk to All Year Cooling about the ENERGY STAR rating on different brands. Not every AC system is ENERGY STAR certified. You might have to spend a little more money on an energy-efficient unit, but the savings on your electricity bill quickly add up. You’ll spend more initially, but you spend a lot less on utility bills over the years.

All Year Cooling works with you to find the right unit at the right price. We offer all of the above brands and a range of SEER and EER ratings to ensure you get an air conditioning unit that is efficient and cost-effective. Our specialists have years of specialized training and experience and are happy to help you with your AC replacement or new installation. Ask us about our same-day install for new AC units when you call or chat.