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Questions About SEER

Aug. 5, 2009
A question I hear often is how much more efficient is 18 SEER efficiency rated equipment compared to 14 SEER equipment? The answer shocks most contractors. Let’s take a look at efficiency beyond the SEER rating.

A question I hear often is how much more efficient is 18 SEER efficiency rated equipment compared to 14 SEER equipment? The answer shocks most contractors. Let’s take a look at efficiency beyond the SEER rating.

Don’t get me wrong; higher efficiency equipment has many benefits such as higher quality construction, improved warranty, lower noise levels, additional quality components and better control systems. These justify the cost and add to value. It’s also critical that we’re completely knowledgeable about the real efficiency of the products we recommend and sell.

The SEER Math
On the surface, an 18 SEER appears far more efficient than a 14 SEER. From the consumer’s perspective, it appears that if you divide 18 by 14 the increase in efficiency should be about 30%. Is that a truthful representation of efficiency?

If that were true, comparing the retail cost of replacing equipment with 14 SEER or 18 SEER equipment might shed more light on the subject. A quick survey of successful contractors showed the typical difference in retail costs to be well over 40%. Which begs the question is higher efficient equipment really a fair recommendation to those we serve? Add that to the question, “is there really a 30% improvement in efficiency?”

The SEER formula is long and confusing. (See the end of the article to receive a copy of the formula.) It appears that the primary increase in efficiency is found by extending the run time of the fan and adding the BTUs drained from the indoor coil once the compressor shuts off.

While this adds a significant boost to apparent efficiency, we find it has little effect on real system performance in regions where cooling hours exceed 500 hours per year. The other drawback is if you’re in a humid climate, the moisture removal capabilities of higher efficiency equipment may be considerably less.

Measured Field Efficiency
Tax credits for high efficiency equipment have created a terrific increase in business in our industry recently. We all love it and heaven knows we need the boost in business right now.

However, the results that NCI has received from contractors of their field testing before and after equipment replacement, have shown that replacement equipment SEER efficiency rating has little effect on the installed system performance. This has caused us to tale a second look into equipment engineering data.

The Energy Efficiency Ratio tells a different story about equipment efficiency. The EER formula is simpler and is more realistic in my opinion. In fact, many states have abandoned SEER all together and have found that EER is a far more relative efficiency benchmark.

One interesting fact about cooling equipment efficiency came from reviewing cooling system efficiency ratings from a number of manufacturers. We found nearly everyone that has a 14 SEER cooling system has an EER rating of about 12.0. We also found many higher efficiency 18 SEER systems that had a published EER of around 12.5. This information left us scratching our heads. Where’s the 30% increase in efficiency that the SEER numbers lead consumers to believe?

EER, as you probably know, is the steady state efficiency of a cooling system. It’s a mathematical formula that divides the rated BTU of the equipment by the watts it takes to produce the cooling. So, in round numbers if a 14 SEER removed 36,000 BTU of cooling using 3000 watts the EER would be 12. The formula would also bear out that if an 18 SEER removed 36,000 BTU using 2880 watts the EER rating would be 12.5.

It appears that the difference between a 13 and 18 SEER system, if we only look at EER is only .5 of an EER. If you look at the watts, the difference between the two is only 120 watts. Or in other words a little more than a light bulb. What if your customers heard that statistic?

That’s only a 4% improvement in efficiency. Or is it a 30% improvement in efficiency? Surely there is there more to this story. Consult with your favorite manufacture to get the whole story of their equipment and become confident in your pitch for high efficiency equipment and system performance improvement recommendations.

Rob “Doc” Falke serves the industry as president of National Comfort Institute a training company specializing in measuring, rating, improving and verifying HVAC system performance. If you're an HVAC contractor or technician interested in a free copy of the SEER formula, contact Doc at [email protected] or call him at 800-633-7058. Go to NCI’s website at for free information, technical articles and downloads.