What is a Two-Stage Air Conditioner or Heat Pump?

If you are researching a new air conditioner or heat pump, you may notice a few features that didn’t exist before. One of those is two-stage cooling, and its demand by homeowners is rising!

Two-stage cooling refers to the type of compressor that’s in the outside condensing unit. This feature allows for two levels of operation depending on your cooling needs. For instance, full capacity on hot summer days or part capacity for milder days. It is a great energy-efficient option when compared to a traditional, single-stage unit.

It’s All About Demand!

 Two-Stage air conditioner or heat pump


When you “start” a bicycle with your feet on the pedals, you have to put in a lot of initial effort to get up to speed.  You may even have to stand up to get the pedals going! The same idea can apply to an air conditioner or heat pump turning ON at 100% capacity. A single-stage unit cools at 100% capacity until it reaches your preset indoor temperature and then turns off.

Think again about riding your bike. It takes less energy to maintain a comfortable biking speed than it does to get up to speed. The same concept applies to two-stage cooling. A two-stage heat pump or air conditioner may use 100% full capacity to reach your desired interior temperature.However, it may use part-capacity to maintain your setting as long as possible.

Depending on temperature, your two-stage unit may have to remain at 100% to maintain indoor temperature. This is similar to riding your bicycle uphill — you can’t back off your pedaling efforts or you may get pulled down the hill. Similarly, you have to keep up your power in order to reach your goal!

For example, if the outdoor temperature is 95°F, your system might stay at 100% capacity to reach and sustain 75°F. But if the outdoor is moderately warm, a two-stage system will operate with less capacity to maintain the preset indoor temperature. The limited cooling demand may result in nearly a 35% speed reduction compared to a single-stage heat pump or air conditioner.


Benefits of Two-Stage Cooling

The two-stage unit may seem to run longer than a traditional single-stage unit. However, this part-capacity operation offers energy-saving benefits that you will feel throughout your home:

  • Consistent Indoor Comfort – With its ability to adjust cooling output, your 2-stage unit may minimize the peaks. Besides, valleys of cooling often found with the ON/OFF cycle of a single-stage unit. The lower stage capacity can maintain the pre-set temperature. So it is longer than the system turns off when it reaches the pre-set temperature. This allows for steady cooling comfort in your home.
  • Dehumidification – The extended operation of a two-stage air conditioner or heat pump runs longer. Therefore, it can removes more moisture from the structure of the interior space.  While the main job of the air conditioner or heat pump is to condition the air to a set temperature, these comfort-creating pieces of equipment may lower the indoor humidity level as a by-product of the cooling process.  Better humidity control leaves you with more comfortable interior air. When humidity levels are better, you may increase the set temperature on your thermostat or control system and still be comfortable in your home.
  • Energy-Efficient – You may think that because a two-stage cooling unit operates longer than a single-stage unit that it would use more electricity. However, electricity usage peaks when a system turns ON. The two-stage feature actually reduces the peak start/stop load cycle which reduces the draw on your electricity. The capacity of the air conditioner or heat pump compressor changes to meet the cooling demand and therefore reduces energy consumption.

Full cooling capacity provides indoor comfort on the hottest days of the year. Meanwhile, the extended operation at the part capacity helps maintain the indoor temperature for a longer period of time. Besides, dehumidifies the conditioned air in the process. With two-stage cooling, your unit may help you enjoy steady and consistent cooling when compared to the single-speed unit.