Marine air conditioning for a 45 ft boat
Two units or a two-zone split. The seawater side is shared, which is why the second zone costs far less than the first.
45 ft Boat Cooling Requirements by Climate
A 45 ft hull (13.7 m) is roughly three cabins of accommodation. The sizer works from the volume that has to be cooled and the seawater the unit has to reject its heat into, so the same boat asks for a different machine depending on where it lives.
| Where it lives | Cooling needed | Same in kW |
|---|---|---|
| Tropics — Cairns, Darwin, the Whitsundays | 23,500 BTU | 6.9 kW |
| Subtropics — Brisbane, the Gold Coast, Perth | 20,000 BTU | 5.9 kW |
| Temperate — Sydney, Adelaide, Hobart | 16,500 BTU | 4.8 kW |
7,000 BTU separates the same boat in Darwin from the same boat in Hobart — about the output of a whole small unit. This is why a figure quoted without a climate is not a figure. Run your own case on the sizing calculator; these rows are that calculator with the length fixed.
Air Conditioning System Layout for a 45 ft Boat
Split. Compressor in the lazarette or engine room, an air handler in each cabin.
Supplied and fitted, including the seawater side and the electrical work, ex GST. The equipment alone is $7k–$10.5k of that; the rest is parts and 28–45 hours of yard time.
About $3.69 for a night at anchor or alongside, at 1.92 kW and the duty cycle a closed-up boat actually sees. Roughly the cost of leaving a light on, which surprises most people.
That leaves 2.0 A of a 10 A marina lead and 7.0 A of a 15 A one — for the kettle, the battery charger and everything else aboard.
Prices are ranges computed from the cost model, not quotes. The same boat lands at either end depending on access, how far the ducting runs and what the yard charges.
Marine Air Conditioner Options for a 45 ft Boat
Dometic Emerald split system, Velair Compact i10VSD SMART, Mabru SC12DC — the Split units on this site, closest rated output first. On a boat this size the choice between them is usually decided by where the box will physically fit, not by the specification.
Cabin Layout and Installation Checks Before Ordering
Every figure above is arithmetic, and arithmetic does not know where your locker is. Tell us the boat and the home port and we will tell you whether the numbers survive contact with your layout — including, sometimes, that a wind scoop would fix it for a hundred dollars.