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When you install a new air conditioner, the size of the AC unit is one of the top considerations. But when you ask, “what size air conditioner do I need?”, it is the appliance’s cooling capacity you are referring to. In this article, we will cover the main factors in determining the right sized air conditioner or HVAC system for your home. After all, this is a major investment, whether you’re shopping for a new window air conditioner or central air conditioner.

Importance of Choosing the Right Size Air Conditioner

Homeowners often choose HVAC equipment that’s the same size as their old system. But if the system is running constantly or turning off briefly, goes on and off frequently, or is causing uneven heating and cooling across rooms, it may have been set up wrong. As mentioned earlier, size refers to cooling capacity, which is measured in British Thermal Units (BTUs). It is not dimensional. Rather, BTUs are measured in tonnage. One ton of cooling capacity is equal to 12,000 BTUs.

Tonnage will work against you in these scenarios:

  • Undersized HVAC: Although it may seem like less will result in savings, an undersized HVAC will struggle to keep up with demand. It can run continually, which results in a higher electric bill than if you had a properly sized system.
  • Oversized AC: When it comes to air conditioning, it’s never good to round up. Excess power usage will increase energy bills, and too large a system will cycle on and off a lot. This is not only annoying; it also strains the equipment and can shorten its lifespan.

However, by choosing a right sized AC, you can avoid these problems. You can maximize efficiency as well. To do so, you’ll need to make a simple calculation.

How to Calculate the Size of Your AC Unit

There is more than one way to calculate HVAC size. A simple method you can do at home, and a basic rule of thumb, is to first calculate the size, in square feet, of the area you intend the AC to serve. This can be a single room, an area, or the total space. To complete the calculation:

  • Measure the length and width of the room/space (in feet).
  • Multiply the length of the room by its width.
  • Multiply the total by 25 BTU.

If you have a 12- by 15-foot room, this means you would multiply 12 by 15, which equals 180; and 180 times 25 is 4,500. The right AC would have a minimum cooling capacity of 4,500 BTU.

But while this is a good start, there are other considerations to take into account. A detailed load calculation can help you boost efficiency even more. In addition to the basic room dimensions, it may factor in ceiling height, how much sunlight or shade the room gets, and the number and size of windows and doorways. The type of insulation and how much you have can be included as well. With a central air conditioning system, there is more to consider, as it may serve your entire house, while a window unit is typically used to heat or cool a single room.

If you’re uncertain about size calculations or have questions, it’s best to consult with a professional HVAC contractor.

Contact The AC Hero

At The AC Hero, our technicians are trained and experienced in HVAC repair and helping customers choose the right sized AC for their homes. We are currently open for HVAC installation, replacement, and repair in the DallasFort Worth area, while practicing social distancing and providing no-contact service during the coronavirus pandemic. Our company is conveniently located in North Richland Hills, Texas. Call us today at 817-587-0250 and we’ll answer your HVAC sizing questions or schedule an in-home consultation.

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