Residential Plumbing & HVAC Experts

Two-Stage Cooling: The Benefits

Because single-stage cooling is more than you need most of the time, two-stage cooling offers better comfort control and lower operating costs. A one-stage air conditioner has only a single cooling output: 100 percent all the time, as long as the unit is running. This all or nothing approach has several drawbacks:

  • Once the house is cooled to the desired thermostat setting, the single-stage A/C continues to operate at 100 percent output, causing the unit to cycle on and off frequently and inducing noticeable temperature swings above and below the desired thermostat setting.
  • Single-stage cooling consumes more electricity, particularly on days where temperatures are more moderate and 100 percent cooling output isn’t required.
  • Because the single-stage unit cycles on and off very frequently throughout the day, it incurs wear and tear faster and may have shorter expected service life.
  • Shorter “on” cycles don’t allow enough time for humidity extraction at the evaporator coil to reach optimum levels. A more humid indoor environment feels warmer and less comfortable.

A two-stage A/C incorporates a compressor that operates in two outputs: 100 percent and approximately 67 percent. When the thermostat calls for quick cooling of an overly warm house, the compressor runs at 100 percent output. Once the thermostat setting has been reached, the system automatically defaults to the lower 67 percent output mode.

Here are some reasons why two stages are better than one:

  • When the system downshifts to the lower output mode, it runs more continuously and maintains more accurate temperature control. This fine-tunes indoor comfort, typically keeping the temperature within one or two degrees of the desired setting and eliminating extreme swings.
  • Running at 67 percent output, the compressor consumes about one-third less electricity so cooling costs are reduced.
  • Because the system runs more continuously, the humidity extraction function — an important component of the cooling process — works more efficiently.
  • Frequent on/off cycling is reduced so wear and tear on critical A/C components is minimized and extended service life is more likely.

In the northern San Diego region, ask the professionals at Sherlock Plumbing, Heating & Air for more about upgrading to two-stage cooling.