Understanding A Few Important Terms When Investigating AC Unit Size

21 March 2017
 Categories: , Articles


If you have finally decided to bite the bullet and have a central air conditioning system installed in your home through a place like One Hour Air Conditioning and Heating, then you will need to make a few decisions when it comes to the AC unit. One of the most important is figuring out the best size of the air conditioner. Keep reading to learn about a few different terms that you may hear when choosing the AC unit and what the terms mean. 


A ton is a an air conditioning measurement that seems to relate to its weight. While you may understand that a ton is equal to 2,000 pounds, this does not seem to make a lot of sense when it comes to discussing the size of the air conditioning unit. What you should understand is that the word ton is used to describe the cooling capacity of the unit. Specifically, a ton is used to describe the amount of heat needed to melt one ton of ice in a single day. This measurement is 288,000 Btus of power

You may notice that some of your central AC choices include two, three, four, and five ton options. These units are often described in terms of hourly Btus. Specifically, a two ton unit is a 24,000 Btu per hour unit. In terms of cooling, this means that the air conditioner can remove 24,000 Btus of heat from the air in one hour. 

It may be confusing to understand how tons and Btus can be used to help you size your AC unit. This is indeed confusing. However, there are a number of charts that can help you figure out exactly how much power, or how many tons of energy, you need for the area you live in. The chart also takes into account the area of your home. For example, for an average sized house in a moderately warm area of the country, you should choose a three ton unit. 


While the zone you live in and the size of your house can all be used to calculate the tonnage of the AC unit needed for your home, these things may not always give you an accurate estimation of the cooling power you need. It may be a good starting point, but a professional HVAC contractor will look at many other things. 

To make sure that you are choosing the right sized unit for your house, a detailed analysis will need to be completed. This analysis is called a manual-J or a cooling load calculation. The analysis provides your HVAC professional with several different types of information that include the sensible cooling load. This describes the amount of heat that must be removed from the air during the hottest parts of the day. Latent cooling is the term used to describe the needs of moisture removal. When the cooling needs are considered, calculations are made that take the whole house and each room into account in terms of cooling need. 

Your HVAC professional may also look at the age of your house as well as heat losses and gains when deciding on the best sized AC unit. If drafts and heat gain are an issue, then your HVAC professional may inform you that a larger unit may be wise. However, the air conditioner will be chosen that is energy efficient. In particular, a unit with a high SEER rating may be a good choice to make sure that you are not wasting energy as you use the larger unit. 

If you want to know exactly how the right AC unit may be chosen for your home, then contact an HVAC professional who can complete calculations and inform you about the cooling needs of your house.