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Last month we talked about SEER ratings and what they mean for you. This time we will seek to understand why is air conditioner unit’s cooling capacity measured in tons. Some people find this method arbitrary and confusing because the average person doesn’t know how many tons of cooling they need. Others may even think the measurement is how much the unit weighs! Therefore, having some understanding on the subject could help clear up any confusion.

To fully understand the topic at hand, we must go back in time to get the back story. In the early 1900s, people would harvest ice from various rivers and lakes in the northern states. Back then, gathering ice was an entire profession This ice was then used throughout the year to cool food with ice boxes and even some houses. Even though the ice harvesting profession went away for the most part, ice itself is the building block of measuring cooling capacity.

If you have a one-pound chunk of ice at 32°, it takes 142 British Thermal Units (BTU) of heat to melt the piece into water. Therefore, if it were a ton of ice you wanted to melt, it would take 286,000 BTUs. Assuming it melts evenly over an entire day (24 hours), that gives us 11,917 BTUs per hour. For ease of remembering and calculating, that is rounded up to 12,000 BTUs per hour, also known as one ton of cooling capacity.


Now you know that the cooling capacity measured in tons is based off heating blocks of ice! On the other hand, this does nothing to inform you how many tons of cooling you may need. That is because it must be meticulously calculated and there are many variables that are considered. If you want to know more about cooling capacity or how much AC you may need, contact Beahan’s Heat and Air.

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