Portable vs Installed Boat Air Conditioning
A lot of owners try a portable unit before committing to an install, and there is a fair amount of marketing aimed squarely at them. Here is what each option actually does, without pretending the cheap one is never the right answer.
The short answer: a portable can make one cabin sleepable on a mild night and will not cool a boat. A domestic split system does not belong on a vessel. An installed marine unit is the only one that removes real humidity from a whole boat in a Queensland summer.
Which of those three you need depends entirely on how hot it actually gets where you are.
Portable, Domestic Split and Marine Air Conditioners
Small, low-wattage units aimed at cooling a person or a berth rather than a space. Some run on a few hundred watts, which a modest bank or generator can carry.
For: cheap, no install, no holes, comes off the boat in winter, works on a small inverter.
Against: cools a berth, not a boat; limited dehumidification; needs somewhere to put the heat and the condensate.
A household unit fitted to a boat. It comes up constantly because the price looks irresistible next to a marine system.
For: cheap capacity, familiar, available everywhere.
Against: air-cooled condenser needs airflow a boat cannot give it; not built for salt; the outdoor unit has nowhere to live; corrosion is quick and warranty is void afloat.
Water-cooled, built for salt, ducted to where you need it, and sized for the boat.
For: cools and dries the whole boat, works at 30 °C ambient, reverse cycle for winter, adds no clutter.
Against: the cost, a hole below the waterline, and a system to maintain.
Domestic Air Conditioner Installation Limits on Boats
This is the one we would push back on hardest, because the price difference makes it genuinely tempting and the failure is not obvious on day one.
A domestic system rejects its heat into the air through a condenser that expects to sit outside in open air. On a boat there is nowhere with that airflow — a lazarette or a cockpit locker recirculates its own hot air, and the unit progressively loses capacity as it heats its own supply. Meanwhile the coil and the casing are made for suburban air, not salt-laden air. Corrosion is fast, the electrical side is not built for a marine environment, and no maker will honour a warranty on a vessel.
Marine units are water-cooled for exactly this reason. They dump heat into the sea, which is why they can live in a sealed locker with no ventilation at all and still work at full capacity on the hottest day.
Portable Boat Air Conditioning for Temporary Berth Use
Temperate coast, a few hot weeks a year. Sydney south, holiday use. Spending five figures to fix a dozen uncomfortable nights makes no sense.
You want to test the idea. A portable for a season tells you whether it is heat or ventilation you actually have, before you cut a hole.
A boat too small to install one properly. Under about 28 ft, a portable and a wind scoop is often the whole realistic answer.
You are chasing sleep, not comfort. Cooling the space around a berth is a smaller job than cooling a boat, and portables are far better at it than at the latter.
Where a portable will not save you: humidity in the tropics. North of about Gladstone the problem is water in the air, and only a properly sized refrigeration system with a condensate drain removes it at any rate that matters.