What is the difference between a Heat Pump and Air Conditioning?

Heat pump vs AC unit comparison

We are asked all the time…what is the difference between a heat pump and an air conditioning (AC) unit?  The answer can range from a highly technical explanation to a simple overview.  Since most of us are not HVAC technicians or physicists, for the purpose of this piece, our explanation will land somewhere in the middle.

The Overview

Heat Pumps and Air Conditioning units use the same basic system; however they are deployed in different ways.

How does an Air Conditioning (AC) System Work?

Think of an air conditioning system as a heat transporter continually moving heat from one area to another, to where it is not needed.

The actual cooling happens when warm air is moved across coils cooled by refrigerant.  At this point, moisture is removed, the temperature is lowered and the cooled air is circulated into your house.

The scientific explanation of cooling is executed through a process known as phase conversion:  when a liquid converts to a gas it absorbs heat.

A simple explanation of how an AC system uses phase conversion to cool air is this:  A compressor pulls refrigerant, in gas form, from the evaporative coil inside your house to the condenser coil located in the external AC Unit.  Here the big fan on your external AC unit pulls the heat out the refrigerant and returns it to liquid form.  Now with the refrigerant back in liquid form, the process begins again.

It is through this endless cycle of refrigerant chilling the indoor air, and subsequent moving of heat outside that keeps your home cool in the hot DFW summers.


Think of a heat pump as a heat transporter continually moving heat from one area to another, depending on the season, to where it is needed or not needed. You will notice that this is the same definition we used to explain an air conditioning unit.  That is because the science of cooling air is the same for a heat pump and an AC unit.  The difference is a heat pump has the ability to reverse the cycle and be used to heat your home in the winter.

When it is warm outside, a heat pump is an air conditioner moving heat out of your house as explained above.  When it is cold outside a heat pump reverses directions and extracts outside heat, transferring it inside.

The question you are probably asking is how can cold air contain heat.  Well, even when the air seems too cold, there are little bits of heat present. You know there is still heat outside when it is cold because it can always get colder.

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    A Heat pump is like a vacuum cleaner that gathers all those little bits heat outside and pulls them inside to heat your house in the exact opposite way it cools your house in the summer.

    One advantage of a heat pump if you are 100% electric is you can save 30%-50% the cost of your heating bill.

    Still have questions or wonder which system is best for your situation?  We want to help.  Contact an Extreme Comfort Advisor today. (972) 234-2336

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