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What Size Ductless Heat Pump Do I Need?

Ductless heat pumps cool/heat only one room or area of your home. So, if you’re planning to use ductless heat pumps throughout your entire home, you’ll need to size each unit according to the room it serves.

So how do you go about doing this?

Well, we’ll give you some general guidelines based on each room’s square footage that will help you predict what size units you’d need.

But know this: Using rule-of-thumbs to size your ductless heat pump is NO replacement for a professional load calculation. You see, a professional load calculation takes into account more than 10 different factors (instead of only looking at square footage) to determine the BTU (British Thermal Unit) output you’d need from your ductless heat pump.

Don’t worry, we’ll explain what “BTUs” are below. We’ll also explain why a professional load calculation is the only way to get an accurate sizing. But first, let’s take a look at general sizing recommendations based on square footage.

Need a professional to determine the size you need? Just contact us and we’ll send a tech right over.

To get a general estimate of ductless sizing, follow these 3 steps...

  1. Calculate the square footage of the room by multiplying its length by its width.
  2. Multiply the area by 25. This answer is the approximate British Thermal Unit (BTU) output you need for that room, which is how ductless heat pumps are sized. Simply put, one BTU represents the amount of energy required to cool or heat one pound of water by 1° F. (Remember: heat pumps can both heat AND cool your home.)
  3. Repeat steps 1 and 2 for each room that needs a ductless unit.

To make it easier, we created a shortcut ductless sizing chart for you:

ductless heat pump sizing chart

But here’s the thing: Those 3 steps above will only give you a rough estimate of the ductless heat pump size you need. This “shortcut” doesn’t take into account all the factors that affect HVAC sizing.

We’ll explain more below...

Square footage isn’t the only factor that determines the size you need

Oftentimes, we work with homeowners who used rule of thumbs (like the one described above) to size their ductless units. But after our techs perform a “load calculation” they’re shocked at how far off their estimate was.

You see, during a professional load calculation, a tech should take into consideration a wide range of factors, 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’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 insulated is the room?
  • 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?

So, do these factors really make a difference? Absolutely.

Examples of how much these factors can affect sizing:

  • If your ceilings are over 8 feet tall, you should increase your estimated BTU output by 20%.
  • If the room is poorly insulated, you should increase your estimated BTU by 30%.
  • If your city’s temperatures often exceed 90° F, increase your estimated BTU by 30%.

Those are just a few examples of how only looking at square footage can lead to incorrect BTU output.

Need a professional to perform a load calculation?

If you live in the Minneapolis area, just contact us.

We’ll send over a tech who can inspect your home and conduct a load calculation to determine the size ductless heat pump you need.