Houston Heating, Cooling, and Electrical

What Are Air Conditioner SEER Ratings?


SEER ratings stand for seasonal energy efficiency ratio, and they are a single-number metric for determining an air conditioner’s operational efficiency. SEER ratings are calculated by comparing an air conditioner’s cooling output and its energy usage. In short, the less energy an air conditioner needs to produce one unit of cooling, the higher its SEER rating. Higher ratings mean better efficiency.

Specifically, SEER ratings look at how many watt-hours an air conditioner needs to output one British Thermal Unit (BTU) of cooling. There’s a lot of math involved, which is why the industry has reduced it down to a single number.

SEER ratings have been around since the late 1980s, and legislation made them mandatory starting in 1992. The minimum SEER rating for air conditioners then was 10, but it’s since been increased to 12 or 14, depending on where you live. In the Houston area, the minimum is 14 because the climate requires homeowners to operate their air conditioning system for longer.

When buying a new air conditioner, the SEER rating is an important number to consider, but it shouldn’t be the only factor involved.

Is it always better to buy an air conditioner with a higher SEER rating?

For some homeowners, it makes sense to invest in an air conditioner with a higher SEER rating. For others, it may be more prudent to stick with a lower SEER rating. Which one makes sense for you? Before choosing a new system, here’s a few things to remember regarding SEER ratings:

SEER ratings are maximum, not average ratings

Think of SEER ratings like a mileage-per-gallon rating for a car. A vehicle that gets more miles per gallon will, on average, get more out of every drop of gas, but if it’s not being operated properly or if conditions are poor, the engine won’t achieve that efficiency. Similarly, a high SEER rating means the system will provide more cooling per watt on average, but if the thermostat is constantly adjusted or if the air conditioner isn’t properly maintained, it won’t get close to optimal efficiency.

An air conditioner with a low SEER rating is still efficient

Compared to an air conditioner with a 20 SEER rating, one with a 14 SEER rating may seem inefficient, but that’s the wrong comparison. If your home is in need of a new system, even a jump to a 14 SEER rating will likely offer a big boost in efficiency, as older systems may have SEER ratings of 10 or below. What constitutes a budget air conditioner today is still much more efficient than systems from 10 or 20 years ago.

Higher SEER ratings will save owners money

It’s difficult to calculate exactly how much money a higher SEER rating will save, but the savings are noticeable. Over the system’s life, higher SEER ratings will save thousands in reduced energy usage.

An air conditioner with a higher SEER rating costs more upfront

Like with most technologies, the more efficient it is, the more it tends to cost upfront. That’s also true of air conditioners, and the initial cost versus expected future savings should be compared before making a purchasing decision.

Are air conditioners with a high SEER rating built with better components?

A higher SEER rating means better efficiency, but it doesn’t mean better quality components. HVAC manufacturers use the same component quality in all of their systems, so a higher SEER rating doesn’t mean the air conditioner is more durable. The most significant difference between low and high SEER rating systems is the size of the coils they use and the type of compressor they operate. In higher SEER rating systems, the coils are usually larger to cover more surface area.

Higher SEER ratings are also achieved with a variable speed compressor, which may be worth considering for your property.

What is a variable speed compressor?

There are three kinds of compressors in modern air conditioners, including single-stage compressors, two-stage compressors and variable speed compressors. Here’s a closer look at all three:

Variable speed compressors

A variable speed compressor is one that can operate at different capacities, depending on how the thermostat is set to and how much cooling is needed. Variable speed compressors use an inverter to control the amount of voltage delivered to the system, so it only consumes the energy it needs.

Most of the time, a variable speed compressor operates at less than 100 percent capacity. It may only function at 30 percent capacity or so, for example, but operate for longer periods of time. This may seem counterproductive, but most of the energy a compressor uses is spent when switching the system on or off. By keeping the system on longer, but at a lower capacity, less energy is spent to produce a comfortable climate in the home.

Variable speed compressors are much better at removing humidity from the home, as it takes longer to drop humidity than it does temperature. Further, variable speed compressors can operate at hundreds of different stages to maximize efficiency.

Two-stage compressors

Two-stage compressors are an intermediate between single-state and variable speed compressors. They can operate at max capacity or at a reduced capacity, but nowhere in-between. A two-stage system can adapt to changing conditions, but not to the degree that a variable speed compressor can.

Single-stage compressors

A single-stage compressor is the oldest compressor technology still in use and has been the standard for decades. These systems are either on or off, so when switched on, they operate at maximum capacity until they hit their target temperature, then they shut off.

What else should homeowners look for, in addition to SEER ratings?

SEER ratings are an important metric, but not the only factor to consider when choosing an air conditioner. There are many others, including:

The size of the air conditioner

The single most important thing to remember when buying an air conditioner is sizing it properly. An air conditioner’s size is measured in tonnage, which refers to how much cooling the air conditioner can provide. Specifically, for every ton, the air conditioner can output an additional 12,000 BTUs every hour. This is tough to visualize, so there are rough recommended values depending on where you live and the size of your home. For Houston homeowners, the hot and humid climate means most homes need larger air conditioners to provide adequate cooling.

However, if the system is too large for the home, it will cool the house too fast, causing it to switch on and off too rapidly. That will result in added energy costs and more humidity in the home.

A reputable HVAC contractor can provide a precise measure of what your home needs, so the trick to getting a properly sized system is finding a reputable contractor.

Your choice in HVAC contractor

The vast majority of HVAC manufacturers produce quality systems and the technology is standard across the industry. The quality among HVAC contractors is less consistent. It’s more important to find a contractor you trust than an HVAC brand you prefer. What determines system life more than anything is how well the air conditioner is installed. If it isn’t installed properly, it will likely break down within a few years, requiring expensive repairs or an early replacement.

Is a maintenance agreement available?

The second-most important predictor of system life is whether the air conditioner is properly maintained. Annual maintenance is recommended to keep your system in good shape, and with proper maintenance, you can expect your air conditioner to last 10 to 15 years. A reputable HVAC contractor will back up their work by offering a maintenance agreement. With an agreement in place, a technician will inspect your air conditioner regularly, perform routine maintenance and ensure there are no major issues that require additional attention.

SEER ratings are a valuable piece of information and should be among the first things you look at when purchasing a new air conditioner. However, these ratings are only part of the picture, and a reputable HVAC company will be able to provide additional information that can help with your decision on which air conditioner to go with.


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