Window Air Conditioners vs. Central AC: Which Option Is Cheaper to Run?

You have a number of different options when it comes to cooling your home in summer. This includes window air conditioners, portable ACs, central air conditioning, ductless AC, and even evaporative coolers or fans. Which option you choose makes a difference since not all of them work as well and some use more energy than others. If you’re trying to decide between window ACs or central air conditioning, this article will compare the two so that you can make a more informed decision.

Comparing Window Air Conditioners and Central AC Systems

If your home doesn’t have central air conditioning, window air conditioners as well as portable AC units are a decent option for keeping your home cool. The issue is that even if you have a small home, you’ll usually need at least two or three window or portable units running to keep it sufficiently cool. The other problem is that most of these units consume a lot of electricity since they’re not all that energy efficient. Most medium-sized units that would be sufficient for cooling areas like living rooms and bedrooms use around 800 to 1,500 watts of electricity per hour (0.8 to 1.5 kilowatt-hours).

A window air conditioner is a good option if you only need to cool a small space, but it takes them a much longer time to cool a larger space. That means that if you want to use multiple window units to cool your entire house, the total electricity consumption will quickly start adding up.

The general rule is that you want around 20 BTUs or British Thermal Units of air conditioning per square foot. That means you’d typically need around 30,000 BTUs to cool a 1,500-square-foot home. For a home this size, you’d usually need either a 2.5- or 3-ton central AC since 1 AC ton equals 12,000 BTUs of cooling. The power draw of a 3-ton unit is usually around 3 to 3.5 kilowatts per hour (kWh). That means that a central AC system would almost always cost less to operate compared to cooling your home with numerous window and/or portable AC units. This is partly because you’d need more than two or three window or portable units to cool every room in a 1,500-square-foot house since each unit only cools the surrounding area.

Central air conditioning works extremely effectively since the cool air gets circulated throughout the entire house. They’re also fairly energy efficient, which means that the ratio of their cooling output to energy consumption is quite high. In other words, window and portable ACs will always use more electricity to put out the same amount of cooling as a central AC. That means that window and portable units would usually need to run quite a bit longer to ensure each part of your home is fully cool.

A central AC system, on the other hand, will typically only need to run for 15-20 minutes at a time. It would never run for a full hour straight if it’s working properly. Window AC units may not always run continuously, but they can when it’s much hotter out. The difference in how much a central AC system will run compared to a window unit is why just looking at hourly energy consumption doesn’t provide the full picture. The fact that central ACs cool more effectively and don’t need to run as much is partly why they use less energy.

Understanding AC Efficiency Ratings

The two main factors that affect how much any type of air conditioning will cost to run are the size of the unit and how energy efficient it is. The more energy efficient an air conditioner is, the less electricity it will obviously use. Different measurements or rating scales are used to express the energy efficiency of central and window air conditioners. The efficiency of window units is expressed in EER or Energy Efficiency Ratio. EER simply tells you how much cooling a unit puts out per hour compared to how many kilowatts of electricity it consumes in an hour.

Central AC units are rated using SEER or Seasonal Energy Efficiency Ratio. This is similar to EER except that it looks at the total cooling output compared to the total energy consumption over the entire cooling season. The reason that you have to look at these numbers over an entire season is the efficiency fluctuates based on how hot it is outside. That’s because central ACs cool more slowly in hotter temperatures, which leads to them using more energy overall.

EER is equal to SEER x 0.875. As such, 12 EER is considered extremely efficient for a window air conditioner and would be the equivalent of just under 14 SEER. A measure of 14 SEER is the minimum required for any new central AC in Oregon and the rest of the Northern US. Many central ACs are 18 to 20 SEER, and the best models are as high as 28 SEER. That shows you just how much more efficient central ACs are compared to window units.

Why Ductless Mini-Splits Are Also a Good Alternative to Window ACs

A ductless mini-split AC system is also a good alternative to using multiple window units. This type of system is especially a good choice if your home doesn’t have a ducted central HVAC system. Even if your home does have a ductwork system, a mini-split can still be a good alternative to central AC as well. The reason is that ductless mini-splits work even more efficiently, and you can find some systems that are rated at 30 SEER or higher.

A mini-split system consists of an outdoor AC compressor and multiple wall-mounted indoor units known as air handlers. That means you can have one air handler in each room to ensure the system cools your entire house. One major advantage of a mini-split is that it provides zoned temperature control since the air handlers are independent. What that means is that each one will only run as much as it needs to in order to keep the room it’s in at the right temperature. It also means that you can adjust the temperature in each room and save energy by turning off the air handler in an unused room.

This zoned temperature control is one of the many reasons why a mini-split system is often a better alternative to window ACs. A mini-split allows you to only cool the rooms you need to just like you can with window units. The difference is that a mini-split will result in your air conditioning costs being far lower. This is because it will be so much more energy efficient than even the very best window ACs. The only drawback is that mini-splits are fairly costly and usually cost more than a similarly sized central AC.

Reliable HVAC Specialists

If you want to add central air conditioning to your home or install a ductless mini-split AC, you can trust the experts at Revival Heating & Cooling for help. We offer professional HVAC installation services for customers in Portland, OR, Vancouver, WA and all of the surrounding areas. If you’re not sure which AC is best for your home, our experienced technicians will be happy to advise and assist you however we can. We’re also ready to help if you need any HVAC maintenance or repairs. Contact us today to schedule an AC consultation and let our team help ensure that your cooling needs are fully met.