AC System Comparison: Central AC vs Ductless Mini-Split

August 3, 2023
Ductless mini-split system in Seattle, WA

For decades, homeowners in the greater Seattle, WA, area had only one viable choice for efficient residential air conditioning. It was to install a ducted central AC system. However, that could be an expensive proposition for homes that lacked preexisting ductwork. As a result, even by 2021, only 53% of area homes had air conditioning at all — and only 21% of that total had central air. But central AC isn’t the only option these days. Homeowners can also opt for a ductless mini-split AC system. But how should you choose between the two? Here’s everything you need to know about central AC and ductless mini-splits so that you can make an informed decision.

How Does Central Air Conditioning Work?

Central AC systems typically include an indoor and an outdoor unit. The indoor unit includes an evaporator coil, a blower motor, and an air filter. The outdoor unit features a compressor, a condenser coil, and a large fan.

To cool your home, a central air conditioner passes a refrigerant in a liquid, low-pressure state through the indoor unit’s evaporator coil. In that state, the refrigerant’s quite cold, so it readily absorbs heat from any air passing through the coil. The blower motor draws in air from your home via its network of ducts, passing it through the evaporator coil and cooling it. That cool air then gets distributed through your home.

When the refrigerant absorbs the heat, it turns into a warm vapor that travels outside to the outdoor unit’s compressor, which increases its pressure. High-pressure refrigerant vapor gets extremely hot, so when it passes through the condenser coil, its heat naturally travels into the outside air. The large fan accelerates this process by providing a steady flow of air over the coils.

The Benefits of Central Air Conditioning

The main benefit of central AC is its efficiency. It uses a single, large compressor, which is the most energy-hungry part of an air conditioner. This is the main reason why it costs far more to operate multiple window AC units to cool your whole home.

Also, central AC systems are generally quiet, especially inside your home. Plus, they’re quite reliable, with the average central AC system lasting between 15 and 20 years with proper maintenance. All of those traits make central AC systems a cost-effective cooling solution. As a result, central AC is by far the cooling solution of choice in the US, with 75% of all air-conditioned homes relying on them.

The Downsides of Central Air Conditioning

Central AC systems have some notable downsides, however. A big one is that they often provide inconsistent indoor temperatures. This happens because the vents furthest from your indoor unit receive less cool air by volume than closer ones. Plus, the ductwork that central AC requires is an issue for a few big reasons.

The first is that it’s wasteful. In some homes, a central AC system wastes up to 30% of the electricity it consumes through ductwork energy loss. This can result from ductwork passing through uninsulated spaces or air leaks at turns and joints in the duct network. And then there’s the matter of the ductwork installation itself. It’s prohibitively expensive to install ducts in finished walls, so central AC may not be a viable option in homes without existing ductwork.

How Do Ductless Mini-Splits Work?

Ductless mini-splits use the same basic process as a central AC to cool your home. However, they feature individual air handlers in each room you want to cool, all connected to a single outdoor unit. That means they require no ductwork to function. In its place, you’ll find a small bundle of refrigerant lines and electric cables running between each air handler and the outdoor unit.

Inside each air handler, you’ll find a blower motor, an evaporator coil, and an air filter. They’re just smaller versions of what’s in a central AC’s indoor unit. They only need to generate enough cold air for a single room or space. And each air handler is small since they’re designed for wall mounting. In most cases, each air handler features a motorized vent that allows them to direct cool air to different parts of the room as needed. They even have individual thermostats and temperature controls.

The Benefits of Ductless Mini-Splits

Ductless mini-splits boast even greater energy efficiency than comparable central AC systems. Some of that comes from avoiding the ductwork-related energy losses mentioned above. And since they also feature a single large compressor, their outdoor units are just as efficient as their central AC counterparts.

The advantage, though, is that they don’t need ductwork. That makes a mini-split a perfect option for homes that don’t already have ducts installed or for adding AC to home additions and newly finished basements. And they do a much better job at keeping the temperature exactly as you want it. With a mini-split, you can set different temperatures in each room or turn off an individual air handler in a room you’re not using. This makes mini-splits more flexible and often much cheaper to operate.

The Downsides of Ductless Mini-Splits

The biggest disadvantage of ductless mini-splits is that they can cost more upfront to install than central AC. The only time this isn’t true is if you need to install ductwork in your home to support a central AC. Plus, your HVAC installer must place a mini-split air handler in the proper location or it may not cool your home as expected.

Then, there’s the fact that you’ll have to accept wall-mounted air handlers throughout your home. Despite their small size, they’re not invisible and may clash with your home’s décor. And although you can avoid the wall-mounted units and opt instead for recessed ceiling models, this can add even more to your upfront costs.

Making a Smart Choice

Choosing between central AC and a ductless mini-split system almost always comes down to a few simple factors. The first is whether or not your home already has ductwork. If it does, a central AC will be a cheaper option that requires very little disruption to your home to install. Without ductwork, a mini-split is the superior option.

The second factor is the costs involved. If you don’t mind paying a bit more upfront for a mini-split, you’ll enjoy greater operating cost savings throughout its lifetime. But if you’re looking for the cheapest viable air conditioning option, central air’s the right choice.

The good news is that Brennan Heating & Air Conditioning can help you whether you want a central AC or a ductless mini-split. Since 1987, we’ve served the greater Seattle area with quality HVAC services, including system installation, repair, and maintenance. We also handle water heaters, offer comprehensive electrical services, and provide indoor air quality solutions. So, if you’re interested in adding a new AC system to your Seattle-area home or replacing the one you already have, contact the experts at Brennan Heating & Air Conditioning today!

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