What You Need to Know About Single Stage, Two Stage and Variable Speed Air Conditioning

AC Unit

At Daniel’s, we take pride in educating our clients about the systems within their homes. This week, we’re taking on variable speed compressors, which are the latest in AC technology. 

Not sure what the difference is between, single-stage, two-stage, and variable speed air conditioners? Wondering which is best for your home? We’re here to help!

Single-Stage Compressors 

Single-stage compressors switch on when the temperature inside exceeds what you’ve set on your thermostat. For instance, if you set your thermostat to 74 degrees, your AC will switch on at 75 and continue to run until your home is back below 74. Single-stage compressors were the standard for decades, and many Austin homes still use them in their HVAC systems. 

The problem is that single-stage air conditioners always run at full blast, using 100% of their systems, and switch on and off continuously throughout the day. Because single-stage AC’s are all or nothing, they can be very inefficient for homes in hotter climates, since they force your air conditioner to work at full capacity for frequent periods.

Plus, by only working in short bursts, there tend to be hot and cold spots throughout the home. You may notice that one room never gets cool enough while another is consistently colder. Because the air conditioner is only on for a short period, it’s difficult to diffuse the cooling evenly throughout your home. 

On the other hand, if you’ve just started to notice that one room is particularly warm or cool, it may be a sign of a blockage in your HVAC duct system. Air duct cleaning can help the cool air spread evenly throughout your home, but it can only do so much for a single-stage compressor. 

Two-Stage Compressors 

Next, there’s two-stage air conditioners that work a bit better than single-stage compressors. Two-stage compressors can work at two different levels, high and low. While they do cycle on and off less frequently than single systems, they still don’t have the flexibility of a variable speed compressor.

Two-stage compressors are still better at cooling your home more evenly than single-stage compressors, but they’re not in the same ballpark as a variable stage compressor in terms of efficiency. They’ll help keep your home more evenly cooled, but they still work in relatively short bursts when compared to variable speed compressors. 

If you can’t quite swing the variable speed compressor, even with multiple financing options, two-stage compressors are still a better deal over a single-stage compressor. If you live in Austin, we highly recommend getting a new AC unit that has a two-stage compressor at minimum.

Variable Speed Compressors

Instead of firing for an hour to cool your home a few degrees, variable speed compressors run continuously to keep your home comfortable. Basically, instead of random blasts of cool air, you’ll get constant air movement to keep your home from ever going above the temperature on the thermostat, which also eliminates hot and cold pockets.

It might sound like an AC running all day would be more expensive, but variable speed compressors are actually significantly more efficient than single or two-stage compressors. Instead of running at full blast, these air conditioners can run as low as 20-30% of capacity to slowly keep your home cool. 

To put this in perspective, consider you have two homes run by two different compressors. As the day gets hotter, the single-stage compressor will switch on and off more frequently to try and keep up with the afternoon heat. Since it’s running at full blast, it’ll get some rooms cool very quickly and then shut off when it thinks the whole home is at the same temperature. Meanwhile, the variable speed compressor can run at a lower capacity when it’s not too hot, and slowly ramp up as the day goes on. 

This keeps the whole house circulated without the air conditioner needing to play catch up when Austin starts hitting 100 degrees outside!

Other benefits of variable speed compressors include:

  • Effectively dehumidify your home
  • Save money on utility costs
  • Can help increase indoor air quality
  • Help prevent mold and mildew in bathrooms and kitchens
  • Discourage insects and other pests
  • More subdued, consistent airflow

Our local AC contractors highly recommend replacing your old, single-stage air conditioner with a variable speed compressor. If you’re not sure what sort of compressor your AC has, feel free to contact us to find out!

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