Marine AC Runs $15K: Climate Control That’s Worth Every Dollar

Marine air conditioning isn’t cheap—$15,000 or more for a properly sized system on a cruising yacht. But for anyone who’s tried to sleep through a humid summer night below decks, or entertained guests in a 100-degree cockpit, the investment justifies itself quickly.

Why Marine AC Is Different

Your home’s central air won’t survive a week on a boat. Marine air conditioning faces salt spray, constant vibration, extreme humidity, and power constraints that residential equipment simply can’t handle. Purpose-built marine units address these challenges with corrosion-resistant materials, compact designs, and efficient operation.

The marine environment also creates unique cooling challenges. Boats absorb tremendous solar heat through fiberglass and canvas. Engines add heat even after shutdown. And unlike homes with consistent power, boats must generate their own electricity or rely on shorepower.

System Types and How They Work

Self-contained units are the most common choice for boats under 50 feet. Everything—compressor, evaporator, and fan—fits in a single compact unit that mounts in a locker or under a berth. Raw water flows through the system for cooling, eliminating the need for bulky external condensers.

Split systems separate the condensing unit from the air handler, allowing more flexible installation. They’re quieter in the cabin because the compressor mounts remotely, but they require more complex installation with refrigerant lines running between components.

Chilled water systems dominate larger yachts. A central chiller cools water that circulates to multiple air handlers throughout the boat. While expensive and complex, these systems offer precise zone control and simplified maintenance.

Sizing Your System

Marine AC is sized in BTUs (British Thermal Units). Rule of thumb: plan for 1,000 BTUs per foot of boat length, then add capacity for high solar load areas like pilothouses and salons with large windows.

A 35-foot cruiser typically needs 16,000-20,000 BTUs. A 45-foot motoryacht might require 24,000-36,000 BTUs distributed across multiple zones. Oversizing slightly is better than undersizing—an overworked system runs constantly, consuming more power and wearing faster.

Power Considerations

A 16,000 BTU system draws roughly 13 amps at 115V—fine on shorepower but a significant load for a generator. Running air conditioning at anchor requires either a properly sized genset or substantial battery bank with inverter capacity.

Newer inverter-driven compressors offer improved efficiency, using variable speed motors that adjust output to demand rather than cycling on and off. They’re quieter, use less power at partial load, and start more gently—important on inverter systems where surge capacity is limited.

Installation Complexity

Marine AC installation isn’t a weekend project. The system requires raw water plumbing (typically tapping into an existing thru-hull or adding a dedicated seacock), electrical connections, ducting if using directed airflow, and condensate drainage.

Professional installation typically runs $3,000-5,000 depending on system complexity and accessibility. DIY is possible for mechanically capable owners, but mistakes with raw water plumbing below the waterline can sink boats.

Operating Costs

Beyond electricity, marine AC requires regular maintenance. Impeller pumps need annual replacement. Raw water strainers require frequent cleaning. Filters in air handlers should be cleaned monthly during heavy use.

Expect to budget $200-400 annually for routine maintenance on a single-zone system. Repairs—particularly compressor replacement—can run several thousand dollars, making extended warranties worth considering.

Heating Options

Most marine AC units include reverse-cycle heat pump capability, providing both cooling and heating from a single system. Performance drops in very cold water (below 50°F), but for three-season boating in most regions, heat pump operation provides adequate warmth.

For colder climates, consider supplementing with diesel-fired heating. Webasto and similar systems provide reliable heat independent of shore power or generator runtime.

Top Brands and What to Expect

Marine Air, Dometic (formerly Cruisair), and Mabru dominate the market. All produce reliable equipment when properly installed and maintained. Price differences often reflect features like digital controls, inverter compressors, and warranty terms rather than fundamental quality differences.

Budget $4,000-6,000 for a quality 16,000 BTU self-contained unit. Add $3,000-5,000 for professional installation. Multi-zone systems on larger boats can easily reach $15,000-25,000 fully installed.

Is It Worth the Investment?

For coastal cruising in summer, marine AC transforms the onboard experience. Sleep becomes comfortable. Entertaining below decks becomes possible. And the boat remains usable during the hottest months rather than sitting at the dock.

For occasional weekend use in mild climates, the cost may be harder to justify. But for anyone planning extended cruising, living aboard, or simply enjoying summer evenings below decks, marine air conditioning delivers comfort worth every dollar of its considerable investment.