Two-stage air conditioners offer a more efficient, energy-saving way to cool your home. Two-stage cooling means that the air conditioner or heat pump has a compressor with two levels of operation: high for hot summer days and low for milder days. Since the low setting can adequately meet household cooling demands about 80% of the time, a 2-stage unit runs for longer periods and produces more even temperatures.
Longer cooling cycles also translate to quieter, more efficient operation and enhanced humidity control. Compared to a single-stage unit, a 2-stage air conditioner or heat pump can remove twice as much moisture from the air. This is important because when moisture levels are high, there’s a higher potential for mold and other indoor air quality problems.
Two of the most important improvements to modern high-efficiency air conditioners are the 2-stage compressor and multi-speed condenser fan.
During the hottest weather, you may need the full capacity of your air conditioner to keep your home comfortable. During this full-time operation, your air conditioner runs at its maximum efficiency. But during moderate weather your air conditioner will cycle on and off to keep from over-cooling your home. This stop-and-go operation is inherently inefficient, since a lot of energy is wasted during the start-up and shut-down part of each cycle.
Air conditioning units with a 2-stage compressor and a multi-speed outdoor condenser fan operate at lower capacity during moderate weather. This results in cycles that are longer and more efficient. It also allows your system to remove more humidity from the air. When the weather is truly hot, they step up to full-speed operation to ensure your comfort.
Variable-capacity air conditioners are all more efficient than older units, but they work in different ways:
- Some 2-stage systems have two small compressors side-by-side. The first compressor operates alone during moderate weather. The second compressor kicks in only when needed during hot weather.
- The two-piston compressors run in one-piston mode during moderate weather and two-piston mode during hot weather.
- The multi-speed compressors actually turn at two different speeds to match the cooling load.
As A/C units evolve and become more efficient, engineers devise new ways of making them achieve better comfort. Two-stage air conditioners are one such innovation. Variable-speed blowers alter the speed of the blower motor to most efficiently match the output of the air conditioner’s compressor and condenser. This translates into better use of the available amount of cooling, less electricity consumption, and lower energy bills.
You can’t avoid the heat of summer, but with a 2-stage air conditioner you can reduce the cost of cooling your home and gain greater comfort throughout your home. You can learn more about air conditioners at www.energysavers.gov, or check out our demonstration of 2-stage cooling.
Our goal is to help educate our customers about energy and home comfort issues (specific to HVAC systems). For more information about 2-stage air conditioners and other HVAC topics, click here to download our free Home Comfort Resource guide.