Call Now 1-800-404-0371

Resource Center

Definition Series – Capacity

Capacity Definition

In the world of HVAC, we have our own vocabulary that we use every day, but sometimes the words we use don’t translate to our customers. In this blog series, we will cover some of this terminology to help you understand what we mean and why these terms are important to your HVAC maintenance and installation.

For this week’s HVAC term, we define the term Capacity and explain why it might be important to you.


Before we had modern HVAC units to cool our homes, people used to buy large blocks of ice to keep their homes as cool as possible. Once modern heating and cooling systems began to be developed, the manufacturers needed a unit of measurement that would be standard across the industry. So they decided to use measurements of ice and water since those are what many were used to. The standard measurement of cooling refers to how long it would take to melt ice.


Capacity refers to the ability of a heating or cooling system to heat or cool a given amount of space and is measured in tons. Cooling capacity is expressed in tons. A ton is the capacity in relation to melting one ton of ice in 24 hours.

Why is This Important?

If your HVAC system is too small, it won’t be able to efficiently heat or cool your home. If the system has a higher capacity than your home requires, it will heat or cool your home too quickly to spread the air evenly or to dry the air sufficiently. Either scenario will eventually lead to higher utility costs, wear and tear on the system, and will cause even more costs in repairs on top of creating an uncomfortable environment.    

It is advised that you choose the size of your system based on how many tons are needed to sufficiently cool your home. A 4-ton air conditioner is one that can remove 48,000 BTUs of heat per hour from the home. For most people, though, 4 tons means 8000 pounds.

However, let us add that choosing the size of your HVAC unit is not actually as simple as adding up your BTU needs. There are several factors to include such as window amount and/or size, floor plan design, number of doors, etc. Online BTU calculators and anyone willing to give a quote over the phone without actually having inspected your home will not be able to accurately choose the correct capacity for your home needs.

How Middleton Can Help

There are many things to take into consideration when choosing the correct HVAC system for your home. The best option for a homeowner is to consult with a professional HVAC Comfort Specialist who can gauge the correct sized system for your home’s needs. Our Comfort Specialists will take the time to carefully inspect and size your home to give you the best options available to you.

If you are looking into installing a new HVAC system, or if you would like more information on Capacity, or what your system needs to run most efficiently, contact us today online or by phone at 1-800-404-0371.

Powered by Lapero