Selecting a new energy efficient AC

The average American spends roughly $1,000 annually heating and cooling their home, which equates to approximately 40 percent of their total energy usage. If you live in a home with an HVAC system that is more than 12 years old, you could be spending even more. As summer approaches you may be contemplating a new AC unit. Here are a few things you should consider before putting a shiny new box in your side yard.   

1. Can I just purchase a new outdoor unit containing a condenser coil and compressor?   

Central air and heating systems are separate units, but matched to work together. They share many common components, like blowers, duct work and return air grilles. If both the cooling and heating units aren’t matched and sized properly, you won’t get the ultimate performance from your AC equipment.

The most common style of AC unit is a split system, which includes the outdoor equipment as well as an indoor evaporator coil, usually installed in conjunction with your furnace or air handler. During the summer your heating system works in tandem with your air conditioner. Within your AC unit, air is cooled as it is blown over the cooling coil, which is most often connected to the air circulation fan of the furnace that then blows cool air through your ducts for distribution across your home.

One of the many things to think about when considering a new furnace is the motor that runs the electric fan. Older, standard furnace fans use considerably more energy than new energy-efficient ECM (Electronically Commutative Motor) fan motors. An ECM (sometimes called variable speed) fan motor alters its speed as needed to meet demand and optimize output.

2. Initial capital outlay v. lowest monthly energy bills?

High-efficiency air conditioners cost more up front than mid-range or minimum-efficiency units, but they deliver the lowest monthly energy bills and often include additional energy-saving features. High-efficiency 14 to 23 SEER (seasonal energy efficiency rating) air conditioners are a good choice if you want to make a long-term investment, live in an area with a long summer, and are willing to pay more at the time of purchase so you can reduce your use of electricity.

SEER is a measure of a central air conditioner’s efficiency and performance. The higher the SEER, the greater your energy savings can be. Typical SEERs range from 13 to 18, but some new systems carry ratings as high as 23.

Most high-efficiency air conditioners are two-stage units, which operate on high only during hot summer days and low on milder days – up to 80 percent or more of the time. The lower power setting allows the units to work more efficiently and produce more even temperatures in your home when compared to single-stage units. Two-stage units may also feature quieter operation and more efficient humidity controls. Your home may also need ductwork renovations to accommodate a high-efficiency unit, which would add additional installation costs.

Government regulations mandate that new central air conditioners have SEERs of at least 13, and with Duke Energy incentives or government rebates, you may be able to purchase a central air conditioner with mid-range efficiency (14 plus SEER) without having to pay more than a low efficiency unit. A mid-range air conditioner probably won’t feature energy-saving upgrades like two-stage cooling, but when you factor in the purchase price they may be the best value for your home. Many of these units also include extra insulation against noise and more weather-resistant hardware than low efficiency options.

While they are not as efficient as mid-range or high-efficiency central air conditioners, low-efficiency air conditioners are still highly efficient when compared to standard units installed only 10 to 15 years earlier. So, if you’re replacing a unit that is at least 12 years old, then even a low-efficiency unit will likely reduce your electricity usage by as much as half. If you’re on a tight budget and no rebates are available in your state, a 13 to 14.5 SEER air conditioner may be your best choice for overall value.

 3. What size is right for my home?

When considering the size of your new unit, you must remember that bigger isn’t always better – right-sized is the only way to go. Unfortunately, selecting the right size unit isn’t as easy as looking at your current system. Your current system could be sized incorrectly, which could lead to under-sizing or over-sizing your new unit.

A unit that is not big enough will have to work extra hard to try to cool your home and provide the comfort you expect. Installing an over-sized unit can have even worse ramifications, adding unneeded expenses to the project and contributing to moisture-related problems in the future.

Thorough contractors will start with a load calculation – many of them using the Manual J® residential load calculation procedure, the official standard for residential load calculation. Contractors should measure your home and evaluate its insulation, window sizes and quantity, and current internal loads, like lighting and appliances.

4. What else should I consider?

Once the proper system is sized and selected, you should carefully consider your home’s duct work, return air grilles and supply air registers.

Properly installed and maintained duct work may last twenty years or more, but time, heat and humidity can prematurely degrade a duct system’s insulation and efficiency. Ducts also collect contaminates over time that need to be cleaned or removed.

If you purchase a high efficiency AC, you may even consider replacing your duct system to get the maximum benefit from your new system. An evaluation should be conducted to determine that the system is clean and configured in a manner that delivers the proper amount of air to each room.

Your return air grille(s) and supply air registers also play an important role in providing heating and air conditioning comfort. There may be occasions when replacing one or more of these devices creates a noticeable improvement in your home’s comfort.

Return grilles that are undersized can reduce the efficiency of your air conditioning system as well as the comfort in your home. Your contractor should verify that these devices are sized and operating properly and offer suggestions for improved performance.

5. What type of HVAC system qualifies for Duke Energy’s Smart Saver incentives?

Many residential refrigeration technologies qualify for incentives assuming the matched components achieve 14 SEER, can be verified with an AHRI reference number and include an ECM fan motor for the home’s air distribution system: Heat Pump (HP) or AC split systems, HP or AC single package (self contained) systems, geothermal heat pumps including direct geoexchange systems.

To learn more about Duke Energy’s Smart Saver program, please visit duke-energy.com/smartsaver.