What it costs to run a mini split

Ductless mini splits get advertised with efficiency ratings and very little explanation of what those ratings mean once the unit is on your wall. Here's the plain version.

Why they're efficient

Two reasons, neither of them magic.

First, there are no ducts. In a typical ducted system a meaningful share of the air you paid to heat or cool leaks out of the ductwork, or gives up its temperature crossing an unconditioned attic or crawl space. A ductless head delivers conditioned air straight into the room.

Second, the compressor varies its speed instead of switching fully on and fully off. A conventional system is either running at full output or not running at all. A mini split runs at whatever fraction of its capacity the room needs, often quite low. It's the difference between driving at a steady speed and accelerating hard to a stop sign over and over.

What that means on a bill

We're not going to print a dollar figure, because anybody who gives you one without seeing your house is guessing. What we can tell you is where the savings come from, so you can judge whether they apply to you.

• If you're heating a space with electric resistance heat right now, baseboard or a space heater, a mini split will use substantially less electricity for the same comfort. That's the biggest and most reliable win.
• If you're conditioning a room you don't always use, zoning it separately means you stop paying to condition it when nobody's in there.
• If your ductwork runs through a hot attic or a vented crawl space, bypassing it removes losses you've been paying for without seeing.
• If you've got a well sealed house with good ducts and a modern system, the improvement will be real but more modest. Be skeptical of anyone who promises otherwise.

Where they make sense around the Lake

We install a lot of these, and they cluster in specific situations.

Rooms with no ductwork. Converted porches, finished basements, additions, bonus rooms over garages. Running new duct to these is often invasive and expensive. A ductless head isn't.

Older cottages. A lot of the smaller lake houses had ductwork added long after they were built, and it shows. When the duct is the problem, replacing the equipment attached to it doesn't help.

Shops, barns and outbuildings. Detached buildings people are currently heating with kerosene or a space heater. A ductless unit heats and cools, runs on a normal circuit, and mounts on the wall instead of eating floor space.

The one room that's never comfortable. Rather than upsizing a whole system for one problem room, condition that room on its own.

Two things to watch

Sizing matters more here than people expect. An oversized head short cycles, leaves the room clammy, and never delivers the efficiency you paid for.

Installation quality matters even more. The refrigerant lines have to be properly flared, evacuated and charged. Most mini split problems we get called out to are installation problems rather than equipment problems.