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SEER, AFUE and HSPF Ratings in HVAC: Why They Matter

SEER, AFUE and HSPF are a few of the acronyms thrown around in the HVAC industry, but they directly relate to a system’s efficiency, comfort and performance.

SEER, AFUE and HSPF Ratings in HVAC: Why They Matter

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Mark Wilson


October 2nd, 2020

Acronyms tend to be very useful to people within an industry, and very frustrating to those outside of it. So, for example, what are the LIHTC rates for FHA loans? That question may make perfect sense or look like gibberish, and the difference is solely in what you know about a specific financial niche.

The HVAC (another acronym) industry is no different. We understand that, and that’s why we’re here to make things simpler.

Because here’s the rub: not knowing what a LIHTC rate is may never hurt you in life. But not knowing truth from fiction with SEER Rating, or the others we’ll discuss in this article, can cost you when it comes time to purchase your next home heating and cooling system.

All three items we’ll be looking at today - SEER, HSPF, and AFUE - relate to the efficiency of either air conditioners, heat pumps, or furnaces. The numbers used to represent them vary, though, as well as what processes that efficiency rating refers to.

Additionally, these ratings aren’t the only items that matter when it comes to efficiency. Knowing their limitations is just as important as knowing their strengths.

Efficiency in HVAC

What is a SEER Rating?

SEER stands for Seasonal Energy Efficiency Ratio. It’s calculated by the ratio of cooling produced by an air conditioner, divided by its energy usage in watt-hours. This ratio is calculated over the length of a typical cooling season.

SEER ratings in modern air conditioners range from about 13 to 22. Depending on the state you live in, any new air conditioner that’s installed must be at least SEER 13 (in some states it’s higher).

SEER is the acronym that homeowners are most likely to be familiar with. It’s often used as shorthand for the efficiency of a system. However, SEER isn’t the final word in an air conditioner’s efficiency. The rating has some limitations that homeowners should be aware of:

  1. SEER ratings should always be read as “up to” that amount. For example, a 20 SEER system is capable of being up to 20 SEER efficiency. It will not always be at that level, due to variations in conditions.
  2. A high-SEER system that is poorly installed will often be no more efficient than a lower-SEER system that is properly installed. Quality matters when it comes to the installation.
  3. A 13-14 SEER system isn’t necessarily inefficient. To the contrary, many older systems are no higher than about 8 SEER. The savings and comfort difference between those and a 13 SEER system is significant. How significant the difference will be will depend on your previous A/C, but the comfort increase and cost savings can still be profound.
  4. Oftentimes, SEER is only as good as the equipment that it’s paired with. By this, I’m talking about the entire HVAC system, including ventilation, ductwork, and your air handler or furnace. We’ll talk about this more in a later section.

Next, we’ll talk in more detail about why equipment matters regarding SEER. We’ll then discuss your potential cost savings from a higher-SEER system.

SEER and Equipment

Above, I stated that SEER is only as good as the equipment it’s matched to. This is most true when it comes to your blower fan. This fan moves air through your home for both heating and cooling, despite being in the furnace or air handler.

If the fan can’t match the output of the A/C unit, you’re losing out on some of what contributes to SEER.

This is where we get into variable-speed equipment. Often, this is your most efficient HVAC equipment, because it can, for example, give you 100% output (which all systems can do) but also 90% output. Or 80%, or 30%. Or 50.6% (sometimes). The most sophisticated systems have 700+ speed settings!

So, naturally, the fan needs to be able to match these settings, or else you’re wasting energy somewhere in the process. This is why equipment matching is important, and it’s also why variable-speed equipment is capable of producing the highest efficiency.

Other factors like weather conditions can also play a part. A 13-SEER air conditioner will be at maximum efficiency when it’s 90 degrees out and it’s working at full capacity. But if your summers aren’t terribly extreme or you use the unit further into the fall than some homes, your average efficiency will dip some.

Cost Savings Based on SEER

Your exact cost savings depends on several factors, including how much you use your system, and factors listed above like equipment pairing and quality of installation. For example, a home in the southern United States that uses an air conditioner more frequently will see far more cost savings than one in Canada that is only using it for a couple of months of the year. Regardless of SEER rating, at that point, the difference in cost savings will be marginal.

However, your potential savings are more easily expressed as a percentage. The graphic below is a good gauge of potential cost savings. As you can see, upgrading from an older system can produce significant cost differences, while smaller upgrades (say, between 16 and 18 SEER) will be more marginal.

Savings from SEER Rating

This doesn’t necessarily mean that a high-SEER system will “pay for itself” over time. Again, usage rates matter, as do variables like how long you expect to stay in your home. The other side of this coin, of course, is comfort. Higher-efficiency systems will also be more comfortable. So there are intangible benefits as well, all of which should be considered when assessing a potential investment.

What is HSPF?

HSPF stands for Heating Seasonal Performance Factor. This rating is limited to heat pumps. It’s used to calculate their efficiency when they’re heating a home. When heat pumps cool a home, efficiency is measured in SEER, just like air conditioners.

As with SEER, the higher the rating, the more efficient the unit it. The numbers used are different, though. Similar to SEER, the rating is calculated by dividing the heating output (measured in British Thermal Units or BTUs) by the energy consumed.

Modern heat pumps must have an HSPF of 7.7, which is again an average. As temperatures drop in the winter, the HSFP of a heat pump will decline. The 7.7 minimum may go up in the future, as energy standards increase, and in colder climates, a higher HSPF is recommended. The most sophisticated heat pumps can reach 10+ HSPF.

HSPF was developed by the Air Conditioning, Heating, and Refrigeration Institute (AHRI). Far from being arbitrary, though, these ratings allow for standardized practices and benchmarks across the industry. Since higher efficiency is ultimately better for the environment as well, these standards allow the HVAC industry to slowly decrease its environmental footprint, either in response to legislative mandates or simply to meet consumer demand for more environmentally-friendly products.

What is AFUE?

AFUE stands for Annual Fuel Utilization Efficiency. It is a measure of furnace efficiency. AFUE uses percentages (up to 100%) that signify how much usable heat is produced by a furnace. For example, an 80 AFUE furnace will produce 20% waste gas, while 80% of the fuel it burns will go toward heating your home.

It was created by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) and has been implemented as a mandatory rating standard by the Dept. of Energy.

As with the other two ratings we discussed, there are minimum standards for new installations. Depending on the state you live in, the minimum could be as low as 80 or as high as 90. The highest-efficiency furnaces can reach about 98%.

Higher efficiency again necessitates considerations regarding equipment pairing. With furnaces, you may also have to alter your ventilation (traditionally a chimney flue and/or PVC pipe) to account for the difference in efficiency between an older furnace and a new one.

Lower waste again means that you’re not having to pay as much for the same level of heating, but of course, higher-AFUE systems are more expensive to begin with. While most modern furnaces will be much more advanced than older systems (with AFUE often well below 80), whether or not the highest efficiency units are right for you is a choice that will be particular to each home.

When Do Efficiency Ratings Matter?

Efficiency always matters. It’s just not the only thing that matters, as we’ve reiterated throughout this article.

When it will definitely matter is when it comes time to replace your existing HVAC system. That’s when you need to start asking several important questions, including:

  1. How often do I run my A/C or heat pump in the summer and furnace in the winter? Constantly? Only for a few hours a day?
  2. In total, how many months is my HVAC system in regular use? 4-5? 10-11?
  3. Am I budgeting for both A/C and furnace replacement? If not, does my existing furnace or air conditioner limit the type of equipment I can pair it with?
  4. How important are things like precise temperature and dehumidification to me?

There may be other questions, but that’s a good start. So, for an example, if you have a single-stage blower motor in your furnace, it makes zero sense to get a 20 SEER, variable-speed air conditioner. Your existing system isn’t designed to support the variable-speed motor in the A/C unit, so you’d be throwing money away.

However, if you’re replacing both and plan to spend the next 15-20 years in your home, the higher-efficiency systems will become more attractive options.

It’s all very situational, but that’s why understanding these variables can be important to make the right decision for your home.

HVAC Rebates and Tax Credits

Ratings also matter to manufacturers and utility companies. Often, there will be incentives in the form of tax credits and rebates for high-efficiency equipment, which won’t be offered for entry-level equipment.

These offers vary by state, region, and year, so there’s no guarantee of this. But it’s always worth looking into. Your HVAC partner should be able to tell you exactly what incentives are available for different types of equipment.

What are Good SEER, HSPF, and AFUE Ratings?

The minimum standards for new installations for each of these metrics mean that there isn’t going to be a rating that’s “bad.” Chances are, a brand new, properly installed 13 SEER A/C will be a big step up from an older system on its last legs.

Beyond that, “good” is going to be relative to the homeowner. To someone in a large home, in a warm, humid climate, 20 might be “good” and everything else would be less ideal. Other examples abound, but there isn’t a number we can put on your satisfaction with your home’s comfort, environmental impact, and utility bills. Only you’ll be able to do that. Fortunately, there are a lot of options for every SEER, AFUE, and HSPF level, options that can meet a variety of budgets and comfort goals.

If you want to take this informational material out of the abstract and apply it to your home, Fire & Ice is ready to have that conversation with you. Check out our service area below. If you’re in Columbus, Ohio or the surrounding area, we’d love to walk you through your options to find the best fit for you.

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