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Definition Series – BTUs

BTUs 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 terms BTUs 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 measurements of BTUs refer to heating water, and the standard measurement of cooling refers to how long it would take to melt ice, in tons.


A BTU is a “British Thermal Unit,” and in the world of HVAC, it represents the amount of energy (heat) needed to raise one pound of water one degree Fahrenheit. Generally, this is used in the context of how many BTUs per hour a product can add or remove water from the air through this increased heat. One BTU is approximately equal to the amount of heat received from burning one matchstick all the way down.

Capacity refers to the ability of a heating or cooling system to heat or cool a given amount of space. Heating capacity is expressed in BTUs 288,000 BTUs or 12,000 BTUs per hour are required to melt one ton of ice within 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.

It is advised that you choose the size of your system based off a calculation that considers the size of the rooms you are attempting to heat or cool. For example, a room the size of 150 to 250 square feet requires less than 8,000 BTUs, but for a room the size of  350-450 square feet, 14,000 or more BTUs are required. 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 consider. 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 BTU’s, or what your system needs to run most efficiently, contact us today online or by phone at 1-800-404-0371.

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