There are many factors you may consider when shopping for an A/C replacement. If you were happy with your old A/C’s performance and efficiency, you may look at new models of the same size and manufacturer. With today’s high-efficiency A/C systems, however, you would be selling yourself short if you didn’t consider all the elements necessary for a successful installation. These include A/C efficiency ratings, correct sizing, optional controls, and new features that make life much more comfortable.

AC Efficiency Ratings 101

There are various A/C efficiency ratings to consider, and understanding what they are and how they’re calculated can help you decide which A/C to select. You may be somewhat familiar with, or have seen, cooling efficiency ratings, such as 18 SEER and 14.7 EER, for instance, and you may wonder what those numbers mean.

Cooling efficiency numbers are different from heating efficiency ratings (AFUE, Annual Fuel Utilization Efficiency), such as 95 percent AFUE; this is because of the calculation formula. For instance, 95 AFUE for a high-efficiency furnace means that 95 percent of fuel input will be converted to heat energy output. 18 SEER, or seasonal energy efficiency ratio, is a ratio of electricity input in watt-hours to cooling output in BTUs (British Thermal Units). In this case, BTUs represent the A/C’s capacity to absorb heat energy from air, rather than using a combustion process.

This makes A/C ratings a bit more complex. The important note is that no matter the type of A/C rating you’re using, the higher the rating number, the higher the energy efficiency and system performance, and the lower the cooling bill in your Mid-Atlantic home.

Following are the efficiency ratings used for A/C systems that help determine how much your new A/C replacement is going to cost to operate, based on the efficiency of systems that you are considering and your past energy bills:

  • Energy Efficiency Ratio (EER) – The EER of an A/C is a ratio of cooling output in BTUs (British Thermal Units) to electricity input in watt-hours. EER is used to measure efficiency in a steady state over time. EER is useful to calculate the estimated cost of operation of different size A/C systems (e.g., 4-ton A/C, in BTUs) and cooling output required of your home. It also demonstrates why correctly sizing an A/C is so important. If your home only requires a 3-ton A/C, why purchase a 4-ton unit? You would be wasting purchase and installation costs, and the over-sized unit would not reach peak performance, causing diminished comfort and potentially higher cooling bills. EER ratings are often listed in information materials from the manufacturer of central systems and window units.
  • SEER – Like EER, the SEER is a ratio of cooling output in BTUs (British Thermal Units) to electricity input in watt-hours. Unlike EER, the SEER is a measure of the estimated efficiency of the A/C over the course of the cooling season with “weather” variables, such as increased and decreased indoor and outdoor temperatures, factored into the equation. SEER is one of the A/C efficiency ratings used by the federal Energy Star program to determine eligibility for a system to become qualified for the coveted Energy Star seal of approval.

AC Shopping Review

A/C efficiency ratings are an important component for making an intelligent decision when selecting your new A/C replacement. However, it’s not the only element. Make sure your HVAC professional uses Manuals J, S and D for calculating the cooling/heating load of your home, A/C system selection and ductwork sizing.

Manual S for A/C system selection also takes into account various add-on equipment, such as zoning systems and HEPA filtration systems, in how they affect airflow across the A/C components and through the home. You may maximize efficiency gains and home comfort by linking all these systems together with a smart thermostat.

Advanced features for the new A/C replacement, such as variable-speed air handlers and two-stage compressors, are an important element of the equation, since these components adjust airflow and cooling output (refrigerant flow) as needed in real time. Slower and smoother airflow allows the A/C to remain at peak efficiency for longer cycles, rather than quick on/off cycling. (The variable-speed air handler – in some cases, the furnace blower – helps boost heating efficiency, too.)

For more expert advice on A/C efficiency ratings and installation for your Baltimore area home, please contact us at Griffith Energy Services, Inc.

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