Air Quality

Single or Variable Speed A/C Units?

Single Stage, Two stage, or Variable Speed A/C Compressors?

If you have been told you need a new air conditioning system and you are researching the various types of A/Cs, you’ve probably come across the terms single speed, two-stage, and variable speed or variable stage systems. What’s the difference in these types of systems?
Let’s look at these three types of A/C compressor technologies and how they function, their benefits, and the costs.


The A/C compressor is the heart of the system. Its the pump that circulates the refrigerant. The compressor gets a signal from the thermostat when it is time for the system to run. The thermostat indicates what the homes desired temperature should be and it “calls” for cooling when the temperatures in the home rise 2-3° above the set point.

How the Compressor Works:
• A single-stage compressor operates at one speed 100%. It’s either 100% on or its off.
• A two-stage compressor operates at two-speeds, 70% or 100%.
• A variable speed compressor operates and modulates at speeds between 25% and 100%.

Variable speed technology allows the AC to initiate and operate at lower speeds for longer periods of time. When the outside temperatures rise and fall, so does the compressor speed. (Understanding the technology details)

Variable Speed Benefits

The variable speed air conditioner beats out the single-stage air conditioners when it comes energy efficiency and the home’s comfort.
• A single-stage air conditioner has shorter, more frequent on and off cycles. A single stage system can start and stop up to 72 times in a 24-hour period during peak season. That causes a lot of wear and tear on the system.
• A variable speed air conditioner runs more continuously but at a lower compressor speed, which uses less energy.

The most energy consumed in a cycle is when the system is turning on. Because variable speed systems turn on and then modulate up and down in speed vs. shutting completely off, they have fewer on and off cycles and costs less to operate.

System Run Time

Lower speed capacity allows for longer run times in the Variable Speed compressors allowing then to maintain your homes comfort in several ways:
1. Reduced humidity – Longer running times means your system has more time to remove the humidity from the air.
2. Even temperatures throughout your entire home – As the fan blows slower but for longer periods of time, your home benefits from better air circulation and fewer hot/cold spots.
3. Cleaner air – variable speed systems that include products like the Air Scrubber Plus® or UV germ eliminating lights are constantly recirculating and cleaning the air of microbial particles, bacteria and pollutants.

Variable vs. Single Stage Costs

Basic, single stage systems are less expensive upfront than the variable speed system, but in the life of the system you’ll pay thousands more to CPS/GVEC. The variable speed does cost more upfront (2-3k depending on the tons) in the long-run your investment will pay-off with savings in utilities and the maximum comfort benefits. In addition to using 42% less energy, you’ll get consistent room temperatures, less humidity and better filtration. It will take 2-4 years of energy savings to pay the costs difference between the single speed and the variable speed but after the difference is paid, the rest of the years in operations is money staying in your pocket that your are not paying in utilities to CPS or GVEC.

Here’s an example:

If the single speed system is $10,000 and $2,035 a year to operate, cost of ownership & utilities over 10 years is $30,350.

A variable speed system at $12,000 and $1,300 annual operating costs over 10 years is only $25,000 – Savings of $5, 000 over 10 years. or $9,025 savings over 15 years.

If you want the lowest energy consumption & utility cost and most consistent humidity reduction and comfort, a 16-18 SEER variable speed system is our recommendation.

If you are look for something in the middle, in some climates a two-stage system offers two compressor speeds. In milder climates and in the overnight hours a two stage compressor can initiate at 70%. If the thermostat set point can be satisfied at 70% compression the unit will shut off. If not, the 70% will jump to 100% after about 8-10 minutes. 2 stage compressors are a great technology, but it’s not recommended when climates are extremely hot for most of the year. (like San Antonio, TX)

The Trane XV18 & 20, the Carrier Infinity and the Daikin FIT are our top choices for Variable Speed options.

Lease-to-own, Subscription leases and financing:

When finances and budget are tight and you need the most affordable payment options, we have lease-to-own, monthly lease subscriptions, and financing options that can help minimize the out-of-pocket costs of purchasing a new system.

There are several other factors that can influence your decision on the type of system that is best for your comfort needs and your home. Any system purchase is a big investment so all considerations need to be reviewed before making the final decision. The comfort advisers at TemperaturePro San Antonio can help you review all the factors, make recommendations and assist with any questions you may have. Schedule a no-charge, in-home consultation today. (210) 858-5566