What Size Ductless Mini Split Do I Need for My Arizona Home?

2018 Sep 26
Posted in: Air Conditioning
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Most Phoenix techs will say, “Well, it just depends on the size of the room.”

Yes, this is technically correct. But square footage isn’t the only factor to consider when sizing your ductless AC.

To determine what size ductless AC you need, a handful of other factors should be considered, including:

  • How many windows does the room have?
  • How many doors does the room have?
  • Is the room a kitchen space or close to the kitchen?
  • What kind of flooring does the room have: carpet or hardwood?
  • And more...

We know—that seems pretty complex. Don’t worry, though, we’ll break it all down for you by explaining:

  1. How ductless AC units are sized
  2. Why you shouldn’t go off of square footage alone
  3. What happens if your ductless AC is sized incorrectly

Need a professional to size your ductless AC? We can do that, just contact us.

How ductless units are sized

Ductless AC units are sized in BTUs (British Thermal Units)—a measurement of heat. The more BTUs a ductless unit has/is rated for, the more heat it can remove from the room in an hour.

For context, one BTU is equivalent to the amount of heat produced by burning through one match. Residential ductless AC units can range anywhere from 7,000 to 24,000+ BTU/hr.

So really, you want to make sure your ductless unit is sized to remove as much heat as the room takes on throughout the day.

Don’t size a ductless unit based on square footage alone

Why? Well, square footage alone doesn’t give you an accurate picture of how much heat the room gains over time.

To get a more accurate glimpse of how much heat a room accumulates in an hour, answer the following questions:

  • Does the room have one or more windows?
  • Is the room facing South?
  • Does the room have a door leading to the outdoors?
  • Is the room a kitchen space or close to the kitchen?
  • Does the room have carpet (vs hardwood floors)?
  • Does the room get direct sunlight at any point during the day?
  • Is the room poorly insulated?
  • Are the ceilings average in height (8 feet)?
  • Are there any additional heat sources in the room?
  • Is the room typically occupied by 1 or more people?

The more you answered YES to the questions above, the more heat the room probably gains in an hour.

All this said, beware any tech that gives you a ductless installation estimate based on square footage alone. You could very well end up with a unit that’s too big or too small.

Let’s take a look at why oversized or undersized units are so bad…

Why sizing your ductless unit correctly is so important

The good news is that most ductless units can be slightly oversized and still work well. But a ductless unit that is too small won’t be able to remove heat from your room as fast as it needs to.

In other words, an undersized ductless unit will run nonstop and still leave you uncomfortable. Not to mention, you’ll see high energy bills and more frequent repairs due to your overworked ductless AC.

The bottom line is to make sure you pick a skilled tech to size your ductless unit correctly. True professionals will always perform a “load calculation” to ensure correct ductless sizing.

During this load calculation, the tech will measure the amount of heat that enters a room based on factors like:

  • How many windows does the room have?
  • How many doors does the room have?
  • Is the room a kitchen space or close to the kitchen?
  • What’s the climate of the area?
  • What’s the square footage of the room, not including closets?
  • Does the room get direct sunlight? If so, how much and for how long?
  • How well is the room insulated?
  • What height are the ceilings?
  • Are there any additional heat sources in the room?
  • How many lightbulbs are in the room? What kind of lightbulbs are they?
  • What is the usual number of occupants in this room?
  • What kind of flooring does the room have: carpet or hardwood?

This precise calculation allows a professional to determine the exact BTU output you need from your ductless mini split—no more, no less.

Most quality professionals will include a load calculation in the initial installation estimate (we do!).

Need an estimate for your ductless AC installation?

We can help. We’ll send a professional to your home to perform a load calculation before determining the ductless size you need.

Just contact us.

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