Single Stage, Two Stage, Variable Capacity?????

There’s plenty of confusion when it comes to purchasing a new heating and air system for your house. One of the most common and easiest to explain is the difference between a single-stage unit, a two-stage unit, and a variable capacity unit. The image below shows the difference between the three.

Stages Of Variable Capacity

Typically the more efficient systems will be two stage or variable capacity. Less efficient systems will be single stage.

Air Source Heat Pump System

The Lennox single-stage ML14XC1 is a popular choice for air conditioning. For two stages, we suggest the Lennox XC16 air conditioning unit. Variable capacity air conditioning can be accomplished by using the Lennox XC20 model.


The Lennox ML196E is an efficient and affordable single-stage furnace. For 2-stage heating, we suggest the Lennox EL296V. And for variable capacity the Lennox SLP98V furnace.

If you have questions on any of this, please give us a call.