Energy-Efficient AC Systems

Summary – TL;DR

An energy-efficient AC system comes down to a few key characteristics, such as proper installation of the right size unit for your home, insulated and correctly placed ductwork in a centralized system, programmable operation that matches your usage needs, and a few others. Each factor varies depending on the home. Read on to find more.

Why Bother With Energy-Efficient AC Systems In The First Place?

Photo by Tom Fisk from Pexels
If you’re reading this article, we’re guessing you already have an inkling of the benefits of greater energy efficiency for your home and it sparked your curiosity. And there’s a lot to learn about what can be gained from this investment in your AC system!

But we know that the decision to replace or update your system isn’t only made on the benefits. So instead of just rattling those off, we’ll start in the same place most homeowners do when considering a sizable project: by weighing the pros and cons.

Pros of an energy efficient AC system:

hourglass icon
  • You can increase your comfort while lowering utility costs. AC system inefficiencies have a big impact on both those counts. If you have a very old AC unit (think the 1970s), today’s energy-efficient AC units can use up to 50% less energy while providing the same amount of cooling. And even for those homeowners with relatively newer equipment made only 10 years ago, an AC unit upgrade can still shave 20% to 40% off energy costs.
  • You can take advantage of incentives and rebates. With the many programs out there that incentivize home energy efficiency, you have a great chance of getting funds to offset the cost of new equipment and upgrades. (More on that in the last section!)
  • There is potential for flexibility in your approach to installation. You can decide to incrementally upgrade the different parts of your existing system, or install a new system altogether.
  • Efficient equipment–that’s properly installed–improves indoor air quality and airflow. And these are important elements not just for optimal system operation, but also for your and your family’s health.
  • Get a break from constant repairs and mounting repair costs. You can get a fresh start when you switch out your old AC unit–especially if it’s already nearing the end of its shelf life.
  • You can reduce your energy consumption from power plants. According to the US Department of Energy, these energy providers “emit about 3,500 pounds of carbon dioxide and 31 pounds of sulfur dioxide” per year for every air conditioner in the average size home.
  • The newest equipment has some additional perks. The newer AC systems designed for efficiency also come with some great features like overall quieter operation, variable speeds, check filter lights, and easy-to-use smart thermostats.

Cons of an energy efficient AC system:

ac pressure gauges
  • A new AC system is often one of the biggest investments a homeowner can make. And though it pays for itself with time, much of the cost is upfront.
  • Sometimes replacing an old AC means replacing the old furnace as well. Depending on the age of the system you currently have, keeping your ancient furnace could negate the efficiency gained by a new AC in terms of your HVAC system as a whole. So keep in mind that the average furnace lasts around 15 to 20 years.
  • Not all homes are equal, and so neither are AC installations. Historic homes for example, sometimes can’t upgrade to a central air system because ductwork can’t be installed according to preservation guidelines. In those instances, the solution is a ductless system–which can be more expensive depending on the layout of the home.
  • Incremental upgrades might not cut it. When it comes to equipment upgrades, a system assessment may reveal that the efficiencies gained by replacing one piece of equipment are lessened by other inefficiencies, like leaky ductwork, in the system.

How do you strike the right balance for you?

hourglass icon

In the short term, installing a new energy-efficient AC system comes with a sizeable upfront cost. But it also immediately improves the comfort and air quality of your indoor environment while taking a good chunk out of your monthly utility bill.

Choosing to incrementally upgrade your AC equipment, as opposed to taking a system-wide approach, can lessen the upfront cost. But it may prolong the return on your investment if there are other system inefficiencies that aren’t yet addressed.

For both approaches, there are different incentive programs that can offset the cost of the project. And in the long term, those costs will be paid back by months of reduced electricity expenses and far fewer repairs. Over a few years, those monthly savings will make your new, efficient AC system pay for itself.

Do the pros outweigh the cons when it comes to your home and needs? Then read on to learn exactly what goes into an energy-efficient AC system and how to get started!

closeup - two hvac technicians employed by Casey Services working on an American Standard brand AC unit outside

What makes a home AC system energy efficient?

Before we get into the particulars of an efficient system, let’s review how your typical AC system works.

AC 101: How AC systems work

At its most basic level, your AC has only a few key parts and functions. First, warm interior air is drawn into your return ducts. From there, the air moves into the air handler where it’s blown over the evaporator’s cooling coils, which keeps its icy temps due to the refrigerant drawn from the expansion valve.  With the air now cooled, the air handler forces it through the supply ducts throughout your home. Meanwhile, the heat absorbed in the air handler is transferred through the compressor and dispersed outside with the condenser. 

This circuit of air conditioning and heat transfer looks like this:

And this cycle continues, with your system churning out cool air while taking out heated air, until the interior temperature matches what you set on your thermostat. 

There are a few different types of AC systems: split system central air conditioning, packaged central air conditioning, ducted air source heat pumps, and ductless AC units (also called mini-splits). 

Here is an example of how split-system central air conditioning works in a home:


Typical elements of an efficient AC system

Now that you know how your air conditioning works, let’s dive into the features that can level up its efficiency.

Pro tip: Keep in mind that, while some of these features are must-haves for greater energy efficiency, a few are nice-to-haves and may only make sense for some homeowners.

closeup - two hvac technicians employed by Casey Services working on an American Standard brand AC unit outside
  • Correctly sized equipment – The right size AC unit is the foundation of an energy-efficient system–and that is based on your home’s cooling load.A proper cooling load calculation is one of the first steps in an installation and it involves several factors: household square footage and surface area, home location and orientation, the number of occupants, the amount of heat given off by appliances, and more. From there you match the cooling capacity of the unit (or unit size) to your home’s required cooling load.
  • Centralized system – A central air conditioning system helps you avoid running up your utility bills as you run individual units in every room. However, the existing structure of your home, your climate, and your needs and comfort levels could make the ductless (non-centralized) alternatives an efficient contender.
  • Sealed and insulated ductwork – This is also essential for greater efficiency, so the air holds its temperature as it travels to your rooms and you don’t lose cool air and air pressure through leaky ducts.
  • Properly placed supply and return registers – Where conditioned air enters and exits your rooms has a big impact on how your indoor air circulates. Without proper supply and return register placement, you end up with stuffy rooms and an AC working overtime to maintain temperature set points.
    closeup - two hvac technicians employed by Casey Services working on an American Standard brand AC unit outside
    • Zoned systems – By breaking up your home system into “zones,” you can manage the temperature in different rooms or parts of your house independently–which means you can save money by setting back the temperature in areas where there aren’t any occupants.
    closeup - two hvac technicians employed by Casey Services working on an American Standard brand AC unit outside
    • Programmable or smart thermostat – This smart technology allows you to optimize your usage automatically based on your routines and needs, with the potential to reduce energy use by up to 10 percent
    • Skilled system installation – Another must-have, proper installation means you can feel confident all the system parts are working together as designed and for optimal performance. Even all the newest, most efficient equipment won’t save you money if not installed properly.


    Important energy efficiency terms to know

    As you research the systems and equipment that are right for your AC project, you’re going to run across a few key terms that can help you compare your options. Look for these energy-efficiency metrics on the side panel of the AC unit or its manual.
    closeup - two hvac technicians employed by Casey Services working on an American Standard brand AC unit outside
      • SEER: This stands for Seasonal Energy Efficiency Ratio and it captures the average amount of cooling per watt of electricity used. The higher the SEER rating of the AC equipment, the higher its efficiency. Some modern equipment can have a SEER as high as 26, while older units often come in at less than 10. ENERGY STAR requires a SEER of at least 13 to be certified.
      • SHR: This stands for Sensible Heat Ratio and it’s an important consideration here in the south. It captures your AC’s ability to remove moisture from the air.
        It’s written as a decimal that represents the percentage of the AC unit’s capacity working to cool versus working to remove humidity. For example, an air conditioner with an SHR of 0.8 means 80% of its total capacity goes to cooling and 20% goes to de-humidifying.
      • BTU: This stands for British Thermal Unit and it measures how much energy is used to transfer heat in a one-hour time span.
        Or, as HVAC equipment manufacturer Trane puts it, “if you see that your air conditioner has 12,000 BTUs, that means it’s absorbing 12,000 British Thermal Units of heat each hour and moving it outside so your environment inside feels better.” An AC unit with 12,000 BTUs has one ton of cooling capacity (12,000 BTUs = 1 ton)
      • Ton: The size of your air conditioner is measured in tons; however, this metric doesn’t refer to its weight but instead to BTUs. You want the tonnage of your equipment to match your home’s load calculation to make sure it is the right size. Home AC tonnage is typically in the low single digits, ranging from 1 to 5 or more. For technical guidance on proper equipment sizing, refer to the North Carolina residential building code.
      • kWh: This stands for kilowatt-hours and it measures how much energy is used to run your air conditioner (or any appliance) for an hour. You are probably familiar with this term because it’s the base unit of your electricity bill, where you are charged a set rate per kWh. Higher BTUs correspond to higher kWhs.

      How do I get started with an energy-efficient AC system in my home?

      If you are ready to boost the energy efficiency of your home AC system, there are a few straightforward steps to get started. And – if you skip to number four – you won’t have to do them on your own.

      Decide on a new AC system or upgrading your existing system

      Many of the factors that go into this decision are unique to you and your home. The right choice can depend on things like your current system’s configuration and age, the structure of your house, and your budget.

      Get to know the brands for the type and size of AC equipment you need

      Once you know the type of central or ductless AC system you want and your home’s load calculation, you can start comparing equipment brands and models.
      Luckily, there are a few expert resources out there to help you with this, like your contractor and ENERGY STAR. The latter even provides a helpful yearly guide to the most energy-efficient products for your home.

      Look into energy efficient AC unit tax credit and rebate programs

      Here again your contractor can be a big help. But there are also numerous national and local organizations that help homeowners locate and apply for the relevant federal, state, and city incentive programs–like DSIRE based out of North Carolina. This group’s name is an acronym for Database of State Incentives for Renewables and Efficiency–and that’s exactly what they do! You can also check out the the rebate finder from Energy Start


      Partner with the best contractor for your energy efficiency needs

      A great place to start is by looking for an HVAC contractor with the right licenses and certifications. Keep an eye out for terms like NATE (North American Technician Excellence) certified and, of course, ENERGY STAR.

      But making sure their process is up to your standards is just as important. Here is an example of what ours looks like.

      And beyond that, be sure to consider your potential contractor’s customer service: Do they have great references? Ask you thoughtful questions about your needs? Provide detailed and prompt communication? When it comes to AC system projects, it’s okay to be picky.



      checking wiring connections

      If you’re looking for a contractor who checks all the boxes, contact us. We firmly believe quality is a way of life and we strive to make your life healthier and more comfortable through our work!


      Related AC Articles

      AC Maintenance: Condenser Coil

      AC Maintenance: Condenser Coil

      A condenser coil is part of the outside AC unit, rejecting heat in the summer and absorbing heat in winter. Here’s how it’s tested on a maintenance check.

      AC Maintenance: Thermostat

      AC Maintenance: Thermostat

      A thermostat senses the temperature in your home, controlling the AC for YOUR desired temperature. Here’s how it’s tested on a maintenance check.

      Categories - Air Conditioning

      Need AC maintenance?

      Oops! We could not locate your form.