Purchasing a new HVAC system is a big decision. It involves making a significant investment that will affect your comfort and bottom line for years. One of the most essential considerations is the efficiency of the systems you consider. However, the efficiency rating scales of HVAC systems are confusing. When you evaluate your options, you’ll encounter an array of acronyms that you may not recognize. Understanding how they work individually is challenging. Comparing between them is even more complicated. That is unless you have the following guide handy to explain things.
Understanding SEER Ratings
SEER ratings apply to air conditioners and heat pumps. Here’s what they are and what they mean.
What Is SEER?
SEER is an acronym that stands for the term Seasonal Energy Efficiency Ratio. It’s a measure that describes how efficient a cooling system is when you use it during an average cooling season. Its inventors are the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) and the Department of Energy (DOE). Those are the same organizations that created AFUE and HSPF ratings, too. SEER’s original purpose was twofold. The first was to aid the federal government in establishing minimum efficiency standards for AC systems. The second was to provide consumers with an easy way to compare the efficiency of their AC options.
How Does SEER Work?
On its surface, SEER seems easy for laypeople to understand. Higher SEER ratings mean you’re looking at a more efficient AC. While true, that fails to convey what SEER ratings tell you fully. For example, did you realize that SEER ratings aren’t linear? Each step up on the scale doesn’t represent the same increase in efficiency. The SEER system is one of diminishing returns. To understand why, you must begin with how manufacturers calculate SEER ratings.
A SEER rating begins with an earlier, more elementary measure of efficiency called energy efficiency ratio (EER). That’s a raw measurement of efficiency you get by dividing an AC’s BTU output by its wattage. The result is how many BTUs of cooling you get for every watt of electricity consumed. When calculating EER, manufacturers test units with 95-degree Fahrenheit outdoor temperatures and 80-degree indoor ones.
In the real world, however, you don’t always use your AC at its maximum output. That’s where SEER comes in. It takes an AC’s EER and applies it to simulated real-world use conditions. Those conditions are as follows:
- 1% of seasonal use at 100% output
- 42% of seasonal use at 75% output
- 45% of seasonal use at 50% output
- 12% of seasonal use at 25% output
SEER ratings are the number that results when you plug an AC’s EER into the equation representing those conditions.
Comparing SEER Ratings
If you want to use SEER ratings to make informed AC purchase decisions, you need a formula to compare them. It will tell you, as a percentage, the difference in efficiency between any two SEER ratings. That’s valuable information that can tell you if the added expense of a more efficient AC is worth it.
The formula itself is simple. Take the higher SEER and divide it by the lower one. Then, take the result and subtract one from it. When you multiply the number you get by 100%, the answer is the efficiency difference between the two ACs. You can also use the same formula to compare the cooling efficiency of a conventional AC with that of a heat pump. However, since heat pumps also provide heat, there’s more to consider with them, which we’ll soon cover.
Understanding AFUE Ratings
Unlike SEER ratings, AFUE ratings apply to furnaces and are much easier to understand. Here’s what you need to know about them.
What Is AFUE?
AFUE is an acronym for Annual Fuel Utilization Efficiency. It’s a raw representation of the efficiency of a gas furnace. Gas furnaces always convert the same percentage of input energy to heat, even if they include variable output burners. AFUE tells you that percentage. Regardless of their technical dissimilarities, it enables an apples-to-apples comparison of all gas furnaces.
How Does AFUE Work?
Calculating AFUE is simple. To do it, manufacturers measure a furnace’s total annual BTU output and divide it by the energy consumed. Then, they multiply the result by 100. The answer that yields is the percentage, on average, of how much of its fuel the furnace turns into usable heat. That’s a function of how complete the furnace’s combustion cycle is and how much heat it allows to escape via its flue.
The average furnace operating in Hamilton Township, NJ has an AFUE rating of 80 or 81. As of 2024, the latter is the minimally efficient furnace you can legally install here. However, you will find furnaces available on the market with AFUE ratings as high as 98.7. Those, however, typically feature two-stage heat exchangers, sealed combustion chambers, and modulating burners. They’re also significantly more expensive than furnaces with AFUE ratings in the 80s.
Comparing AFUE Ratings
You can compare the AFUE of any furnace against any other directly. It’s not a diminishing returns scale like SEER. That means a point difference between two units is always the same efficiency gain or loss. That leaves you free to use AFUE and price as your primary deciding factors when buying a furnace.
Understanding HSPF Ratings
HSPF ratings are the efficiency scale for heat pumps operating in heating mode. The following is what they are and how to use them.
What Is HSPF?
HSPF stands for Heating Seasonal Performance Factor. It’s similar to a SEER rating in that it attempts to reflect a heat pump’s efficiency during winter conditions. However, HSPF doesn’t try to simulate a heating season. Instead, it’s an average of a heat pump’s efficiency operating at three typical winter temperatures.
How Does HSPF Work?
Unlike furnaces, heat pumps don’t convert fuel to heat. They collect heat from the outside air and carry it indoors instead. That means a heat pump’s efficiency in the winter is directly related to the outdoor temperature. The colder it gets, the harder a heat pump works, cutting efficiency. The HSPF formula adds a heat pump’s BTU output per watt at 47-, 35-, and 17-degree outdoor temperatures. Dividing the result by three gives you the HSPF.
Comparing HSPF ratings
When heat pump shopping, you can directly compare any system’s HSPF with another’s. The higher the HSPF, the more efficient the heat pump in winter. An efficient heat pump should have an HSPF of at least 8 these days. Any heat pump with an HSPF of 8.2 or higher and a SEER of 15.2 can qualify for ENERGY STAR certification.
Your Local Heating and Cooling Efficiency Experts
With the information above, you can make informed purchase decisions about efficient HVAC systems. But that’s only half the battle. You also need a reputable HVAC company to sell and install your new system. For over 13 years, we’ve been the leading HVAC company in Hamilton Township. We sell, install, repair, and maintain HVAC systems of all kinds. We also offer commercial HVAC and indoor air quality services. We can even provide financing on approved credit to help you pay for a new system. So, when you’re ready to upgrade to a new, efficient HVAC in Hamilton Township, call the experts at Conway Comfort Heating & Cooling.
