Ducted vs ductless heat pumps: how to choose

If you've started shopping for a heat pump, you've probably noticed two categories of equipment that look quite different. A central ducted system has a large outdoor unit, an indoor air handler in your basement or mechanical room, and supply registers in every room. Just like a furnace. A ductless system, often called a mini-split, has the same outdoor unit but one or more wall-mounted indoor heads that blow air directly into a room.

Both heat your home. Both are heat pumps. Both qualify for most provincial rebates. The decision between them comes down to your home's existing infrastructure, your floor plan, and how much you care about how the equipment looks.

Ducted central systems

A ducted heat pump uses your home's existing duct system to distribute conditioned air. The indoor air handler sits where your furnace currently sits, and the same supply and return ducts carry warm or cool air to each room. Often the heat pump replaces both the furnace and any existing central air conditioner, leaving you with one piece of equipment doing two jobs.

This works well when:

• You already have good central ducts sized for adequate airflow.
• Your home is a typical layout with rooms branching off a central trunk.
• You want the equipment to be invisible: no wall units, no visible refrigerant lines.
• You're replacing a furnace and you want the simplest transition.

It doesn't work as well when:

• Your existing ducts are undersized, leaky, or in poor condition.
• You don't have ducts at all (radiator-heated home, electric baseboard home, hydronic floor system).
• Specific rooms have very different heating or cooling needs from the rest of the house.

The duct sizing problem

Many older Canadian homes have ducts that were sized for furnaces, which produce hotter supply air. A heat pump's supply air is cooler (around 32°C versus 45°C for a typical furnace) so it needs more airflow to deliver the same amount of heat. Pushing heat-pump airflow through furnace-sized ducts creates pressure, noise, and uneven distribution.

A good contractor will inspect your ducts before quoting a ducted heat pump. A duct evaluation might recommend:

• Upsizing the main trunk line (significant work).
• Adding additional supply runs to specific rooms.
• Replacing undersized return air paths.
• Sealing duct leaks with mastic or aerosolized sealant.

Duct modifications can add $1,500 to $5,000 to a heat pump install. Some contractors will quote a ducted heat pump without inspecting your ducts; if the resulting install is loud, drafty, or uneven, you've inherited a problem that's expensive to fix after the fact.

Ductless mini-splits

A ductless system uses one outdoor unit connected to one or more indoor heads by refrigerant lines. Each head is essentially its own air handler. It has its own fan and pulls air directly from the room it serves.

This works well when:

• Your home has no ductwork (electric baseboards, radiators).
• You want to heat or cool specific zones independently, like different temperatures in bedrooms versus living areas.
• You're adding heating or cooling to an addition or a space that has no easy duct access.
• You want the most efficient possible system (ductless avoids the 10–20% energy loss that ducts often introduce).

It doesn't work as well when:

• You have many small rooms, where placing a head in every bedroom, bathroom, and closet gets expensive.
• You want the equipment hidden, since wall heads are visible.
• You want a single thermostat controlling the whole house.

How many heads do you need?

A common mistake is to install one mini-split head in the open living area and hope the heat finds its way to the bedrooms. It usually doesn't. Heat doesn't flow well through doorways and around corners. Bedrooms with the door closed at night end up cold. Bathrooms become problem zones.

A general rule is one head per zone, where a zone is a continuous space with a similar load. An open kitchen-living-dining area is one zone. Each bedroom is its own zone. A finished basement is its own zone. A typical three-bedroom home ends up with three to five heads.

Multi-head systems use a single outdoor unit that serves all the indoor heads. The wiring and refrigerant routing gets more complex, but the equipment cost per head drops compared to having multiple separate outdoor units.

The hybrid option: ducted mini-split

There's a third category that gets less attention. A ducted mini-split (sometimes called a "concealed-duct" or "slim-duct" unit) is a small ducted air handler that fits in an attic, ceiling cavity, or above-ceiling soffit and serves a few rooms through short duct runs. It combines the invisibility of a ducted system with the zoning of a ductless system.

For a renovation or addition, a slim-duct head can serve a master bedroom plus an ensuite plus a walk-in closet from a single indoor unit with short ducts running through the ceiling space. It is more expensive than a wall head per zone but cheaper than retrofitting full central ducts.

Cost comparison

Installed costs vary significantly by region, contractor, and home complexity, but typical Canadian ranges are:

These are pre-rebate numbers. Provincial and federal rebates can reduce the net cost substantially, but they typically apply to the equipment side and not to duct modifications.

Performance differences

Ductless mini-splits are slightly more efficient than ducted systems in practice. The conditioned air goes directly from the indoor coil into the room, avoiding the 10–20% energy loss that ducts cause through leakage and heat transfer to unconditioned spaces. They also let you heat or cool only the rooms in use.

Ducted systems offer better humidity control (the larger air handler removes more moisture per cycle in summer) and more even temperatures across all rooms. They are also better at integrating with a smart thermostat, an HRV, or whole-house filtration.

Neither system is dramatically more efficient than the other once you account for installation quality. A well-installed ducted system in a leaky-ducted house performs worse than a well-installed ductless system. A well-installed ducted system in a tight, sealed-duct house performs about the same as ductless.

The decision tree

If you have ducts in good condition: ducted is usually the right choice. It's invisible, single-thermostat, and integrates with whatever else you have.

If you have no ducts: ductless. Don't try to retrofit ducts into a baseboard-heated home unless you're doing a major renovation anyway. The cost is rarely worth it.

If you have ducts but they're undersized or leaky: get a duct evaluation. If duct repair pushes the total cost above ductless, go ductless.

If specific zones need very different temperatures: ductless or a hybrid system. A central ducted system gives you one thermostat for everything.

If you're doing a major renovation: this is the best time to install proper central ducts and a single ducted heat pump, because the walls are already open.