Pros and cons of ducted air conditioning

We’re loving our new central ducted air conditioning. (I was almost disappointed when the Sydney heat wave ended and we didn’t need it for a few days). Ducted air conditioning consists of a large outdoor unit (compressor) connected to a large unit inside your attic with ducts that supply the air to each room.

Pros

• Powerful: Our unit is about the smallest available at 8.8 kw (meaning kilowatts of cooling power, not of electricity consumed), which covers our 3 small bedrooms easily on 40 degree days, and eventually cools our whole 100m2 3 bedroom house when it’s 35 degrees outside. For larger (or less shaded and insulated) houses, standard units go up to about 27kw (beyond that, I think you’d need to look at commercial AC).
• Reliable: 5 year parts and labour warranties are standard and units are expected to last about 25 years. Split or window units generally won’t last as long, and more units means more moving parts, and often greater servicing and repair costs in the long run.
• Unobtrusive: The ceiling ducts in each room are less noticeable and more attractive looking than the inside part of a split-system, window/wall, or portable air conditioner. This affects more than just aesthetics if your rooms don’t have a good spot for a split (Our bedrooms are quite small – about 4m x 3m with large windows – one of them would have needed a pretty complex installation, at significant extra cost). The outside unit (the compressor) is quite large (about 1.5m high and 1m wide) but a single unit cools the whole house, and you can put it around the side or back of your house.
• Flexible: With at least 2 “zones” (we got 4, some installers will add extra zones cheaply) you can often cool just the rooms you’re using, to save energy and/or cool rooms down faster. I enjoy coming home on a 40+°C day, turning the AC on at full power, but only with the “bedrooms” zone open, so the bedrooms cool down to 25°C in about 15 minutes.
• Quiet: The volume level ranges from “silent” to “noticeable” depending on the fan speed setting and how many zones are open (though the outdoor unit can be noisy if you are outdoors when it’s on)
• Good technology: As ducted is expensive, ducted units tend to be good brand units with quality construction and recent technology. Most are reverse cycle (heating in winter as well as cooling in summer) and inverters (able to use less power when it’s not needed, so more efficient). Most dehumidify the air, some purify it too.

 

Cons

• Expensive: prices start at about $5000 to purchase a small, cheaper (less established brand) unit and install in a single-story 2 bedroom house. We got a top-brand Fujitsu unit (with a free lawnmower) for $5800 (installed with 7 outlets and 4 zones). Larger (or less shaded/insulated) houses can easily cost 10 to 15 grand, sometimes more. A ducted system can also cost more (than equivalent-power high quality split systems) in electricity, but only if your roof space is hot (because the ducts aren’t perfectly insulated) or if you end up cooling more of the house than you would with splits (due to having too few / too large zones, or zones that include spaces you don’t always use at the same time). For larger units (about 18kw and above) you will need 3-phase power in your home. If you don’t already have it, that can add another $1500 or more to the cost.

Hope this helps someone. If you have anything to add, please let me know in the comments.