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How Do Ductless (Mini-Split) Air Conditioners Work?

A ductless mini-split air conditioner works like a regular central air conditioner but without the ducts. 

How’s that possible?

  • The indoor unit blows warm air from your home over cold evaporator coils. The refrigerant running through these coils absorbs the heat from the air and brings it to...
  • The outside unit is where the refrigerant dumps all the heat it pulled from your home’s air.

Now in a regular split system air conditioner, the indoor unit is in the attic or closet. Ducts carry your home's air to this central location, where it is cooled and then returned to your home via more ducts.

But in a mini-split ductless system, the smaller indoor unit is actually in the room it’s cooling.

Ducltess mini-split in a Sarasota home

A Mitsubishi wall-mount indoor unit. Photo credit Mitsubishi Cooling & Heating (we added the red circle) 

The indoor unit being in the room eliminates the need for air ducts. The indoor unit simply pulls in warm air from the room it's in and blows cold air right back into the room.

“But can a ductless system cool a whole home, then?”

Good question. Yes, it can. 

Here’s how: Multiple indoor units can connect to a single outdoor unit to provide air conditioning to your entire home. 

And there are a variety of indoor unit styles to fit different rooms. You’ve already seen the wall mount above. But there’s also:

Ceiling recessed

Ceiling recessed ductless mini-split air conditioner

Photo credit: Mitsubishi Cooling & Heating

Horizontal ducted

Horizontal ducted mini-split

Photo credit: Mitsubishi Cooling & Heating

Floor mount

Floor mount ductless mini-split

Photo credit: Mitsubishi Cooling & Heating

“Ok, but why would I want a ductless air conditioner?”

A mini-split ductless air conditioner can has several advantages over a traditional central AC. Namely:

Easier installation if you don’t have ductwork

If you’re adding AC to a room or home that doesn’t already have ducts, mini-split systems can be a great alternative to the expense of installing a bunch of ductwork.

Can both heat and cool

Most ductless mini-split systems are heat pumps. That means they can both heat and cool your home, eliminating the need for a separate heater. 

Of course, you can get central air heat pumps, but it’s an upgrade.

Related: What is a Heat Pump?

Built-in zoning

Since each area of your home has a separate indoor unit, you can individually control the temperature of each part of your home.

Find out more about zoning in our article, Is a Zoned Heating/Cooling System Right for You?

Better energy efficiency

Ductless mini-split systems won’t lose any cooled air due to duct leakage. And duct leakage is a real problem with central air conditioners. 

In fact, ENERGY STAR estimates that in a typical home “about 20 to 30 percent of the air that moves through the duct system is lost due to leaks, holes, and poorly connected ducts.”

Related: How to Tell if Your Air Ducts Are Leaking.

“Are there any downsides?”

Sure. In general, ductless systems are about 30% more expensive than a central air conditioner—but that’s not including ducts. The basic units also aren’t super attractive, though you can upgrade to the recessed versions.

“How much do they cost?”

  • Energy efficiency rating (SEER) 
  • Size (tons) of the system
  • Number of evaporator/blower units
  • Brand

For an exact price for your home, contact us online or call us at (800) 226-2636 to set up a free, in-home estimate for a mini-split system.

Cool Today provides air conditioning and heating installations to Sarasota, Florida and the surrounding areas like Bradenton, Tampa and Port Charlotte.