Air Conditioner Sizing: A Fairy Tale Lesson in Sizing

Goldilocks and the Three Air Conditioners: a fairy tale story about how to properly size your air conditioner

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Once upon a time in a suburb was a house where Goldilocks lived. The bottom floor was very big, the second floor was middling in size, and only the top floor could be described as a small story.

Each room was a different size too. The living room was very big, the master bedroom was middling in size, and only the entryway could be considered small.

One day, in late May, the sun broke through the cloud cover and unleashed a heat that hadn’t been experienced in Goldilocks’ neck of the woods in several months. As Goldilocks readied herself for the day, a bead of sweat formed on her forehead and slithered down to the bridge of her nose.

“This heat is too hot!” said Goldilocks, who had recently been promoted at her job to project coordinator, which meant some additional disposable income she didn’t have the past summer. It was money Goldilocks could use to buy a central air conditioner instead of relying on her noisy, uncomfortable window units.

Goldilocks used an internet matchmaking service to find the four best contractor estimates in her area and set out for a new air conditioner.

The first contractor was well respected in the area and offered the lowest estimate. He arrived in a professional-looking van with professional-looking clothes and a shiny new central air conditioner in the back of his van.

“This is the air conditioner you need,” he said. “I can tell just from eyeballing your house, using my past experience, that this is the right air conditioner sizing.”

The contractor walked inside her home and installed the air conditioner, then went on his merry way with her money in hand.

The next day, the heat was even hotter than the day before, but Goldilocks noticed her the top story of her house was several degrees warmer than the other parts of her house.

“This air conditioner is too small!” she said.

Goldilocks called another contractor, another man well respected in his field, who offered a higher price for a larger air conditioner. He pulled up to her home in a professional-looking van wearing professional-looking clothes and a shiny new air conditioner in the back of his van.

“This is the air conditioner you need,” he said. “I can tell just by looking at the square footage of the house that this is the right air conditioner sizing.”

The contractor walked inside her home and installed the air conditioner, then went on his merry way with her money in hand.

The next day, the heat was even hotter outside and Goldilocks’ house was a nice cool temperature. But it felt like a sauna--she was smothered in moisture and humidity.

“This air conditioner is too big!” she said. ‘It constantly turns on and off and can’t effectively reduce humidity. Woe is me.”

So Goldilocks called a third contractor, who offered an even higher price for a middling-sized air conditioner. He pulled up to her home in a professional-looking van wearing professional-looking clothes, but no shiny new air conditioner in the back of his van.

“I’m not sure what size you need,” he said, holding at his side what appeared to be a boring and dense textbook. “But I have with me Manual J: Residential Load Calculation, published by the Air Conditioning Contractors of America that will tell me the right air conditioner sizing.”

“It takes in all factors of your house, including the quality of your insulation, square footage, the individual size of each room, the shading from trees outside your house, the home’s orientation, the area where you live, and more,” he said.

The contractor used his trusty industry standard sizing guide to find the right air conditioner sizing and left her home, only to return soon after with a new shiny air conditioner, which he installed.

The next day, the heat was even hotter outside, but Goldilocks’ house was cool, arid, and comfortable.

“This air conditioner is just right,” she said, smiling.

The moral of the story: Qualified contractors may be established in the area and offer a great price, but no one can correctly estimate the right air conditioner sizing using nothing more than their eyes and experience. An incorrectly sized air conditioner can lead not just to discomfort, but also extra expense on your energy bills. Always hire contractors who rely on industry standard sizing guides to ensure your air conditioner sizing is just right.

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