Marine Electric Systems designs and installs marine air conditioning systems for sailing yachts, catamarans, and motor yachts throughout the Chesapeake — Annapolis, Baltimore, and the greater Washington DC area. Chesapeake summers are humid, hot, and long. A properly sized, properly installed marine AC system is the difference between actually using your boat in July and abandoning it for the season. Done right, the install includes BTU sizing matched to the boat, ducting that delivers cold air where it's needed, seawater cooling that's serviceable for the long haul, and electrical integration that lets you run AC at anchor on battery — not just at the dock.

What's included in a marine air conditioning install

• AC system sized to your boat — typical: 6,000 to 16,000 BTU per zone, with multi-zone systems on larger boats
• Brand-agnostic specification — Dometic, Webasto, Mabru, CruisAir, FlagShip; we recommend the right unit based on boat type, electrical capacity, and how you cruise
• Self-contained, split, or chiller architecture — self-contained for small boats, split systems for medium boats with separate condensing units, chiller systems for large yachts with multiple zones
• Seawater pump and strainer — properly sized, raw-water plumbing with isolation valves, accessible strainer for routine cleaning
• Ducting and grills — sized for proper airflow, insulated where it runs through hot spaces, with adjustable grills at each cabin
• Digital thermostats — one per zone, with humidity control and reverse-cycle heating where applicable
• 120V or 240V wiring — dedicated breakers, properly sized for compressor inrush current
• Inverter-compatible options — for boats wanting to run AC at anchor on battery, we spec variable-speed Mabru units or appropriately sized Victron Quattro/MultiPlus inverters
• Condensate drainage — routed to a sump or overboard, with proper backflow prevention
• As-built documentation — ducting and electrical schematics, full system test, and an owner walkthrough

Why marine AC is different from RV or home AC

Marine AC has to handle three things home and RV systems don't: salt-water cooling, vibration, and the corrosive marine environment. Cooling is done with raw seawater rather than air-cooled refrigerant condensers — dramatically more efficient, but it requires a seawater pump, intake strainer, and copper-nickel condenser coil that can survive years of saltwater contact. The compressor and refrigerant lines have to handle constant boat motion. Every metal component needs to be marine-grade. Cutting corners on any of those is how you get an AC system that fails in three years instead of fifteen.

Self-contained vs split vs chiller — what fits your boat

Self-contained units are the simplest: compressor, condenser, evaporator, and blower all in one box, typically mounted under a settee or in a locker, with short ducts to nearby cabins. Right for smaller boats (single-zone, 30-45 ft) where one unit can serve the whole interior.

Split systems separate the compressor and condenser (typically in an engine room or lazarette) from the evaporator and blower (in or near the cabin being cooled). Quieter in the living space, more flexible mounting, easier to add zones. Standard on cruising boats from 40 to 60 feet.

Chiller systems use a central compressor and condenser to chill a glycol-water loop that's pumped to multiple cabin air handlers. The most flexible architecture for multi-zone systems on large yachts and catamarans — each cabin gets independent control, the noisy hardware is far from living spaces, and adding zones is easier. Higher install cost, but the right answer above 60 feet or for serious multi-zone applications.

Running AC at anchor — what's actually possible

The most common upgrade we see today is making AC work at anchor on battery, not just at the dock. The math is straightforward: a 12,000 BTU unit pulls roughly 1,200W to 1,500W running. On a 1,000 Ah lithium house bank, that's 8-10 hours of AC at anchor between recharges. Two things make it possible:

• A properly sized inverter/charger — Victron Quattro 5000W (or larger) handles the compressor inrush current and the running load comfortably
• Variable-speed AC units — modern Mabru compressors throttle smoothly instead of cycling, drawing 30-50% less power on average than fixed-speed units. Lithium-friendly, inverter-friendly, and dramatically extends anchor-out runtime.

Brands we install

We are brand-agnostic on AC selection. Dometic (CruisAir, Marine Air, Sea Land) and Webasto are the long-standing standards — reliable, well-supported, with strong dealer networks. Mabru Power Systems has become our go-to for owners who want to run AC at anchor on battery, thanks to their variable-speed compressor designs. FlagShip Marine offers strong value at midrange. We'll specify what fits your boat, electrical system, and cruising goals.

Service area

Marine Electric Systems serves cruising sailboats, motor yachts, and catamarans throughout the Chesapeake region: Annapolis, Baltimore, the Eastern Shore, the greater Washington DC area, and the surrounding Maryland and Northern Virginia waterfront. We work at marinas, boatyards, and private docks across the region.

For more on how AC integrates with a full electrical platform that supports running it at anchor, see our marine lithium battery installation and inverter/charger pages.

Frequently asked questions

How much BTU do I need?

Rough sizing rule: 12,000 BTU per 100 sq ft of cabin space, adjusted for hatch sun exposure, hull insulation, and cabin layout. A typical 40-foot sailboat with two cabins runs 12,000 to 16,000 BTU total. A 50-foot motor yacht with three cabins is usually 24,000 to 36,000 BTU across multiple zones. We size based on actual cabin volumes during scoping.

Can I run AC at anchor without a generator?

Yes — with a sufficient lithium house bank, a properly sized inverter/charger (Victron Quattro 5000W or larger), and ideally a variable-speed Mabru compressor. Typical runtime is 6 to 12 hours from full charge depending on bank size, AC load, and ambient temperature. Daytime solar can extend that significantly.

What's the difference between Mabru and Dometic?

Both make excellent AC systems. Dometic's strength is depth of dealer network, parts availability, and time-tested reliability across multiple product lines (CruisAir, Marine Air). Mabru's strength is variable-speed compressor technology that makes anchor-out battery operation practical. The right choice depends on whether you need parts available globally (Dometic) or maximum off-grid efficiency (Mabru).

How long does a marine AC install take?

A self-contained single-zone install typically takes 3 to 5 days. A split system or chiller install with ducting and multiple zones is 5 to 10 days. As part of a full electrical refit including inverter/charger upgrade, AC work integrates into the wider 1 to 3 week timeline.

Will my existing electrical system handle a new AC unit?

Depends on the unit and your existing capacity. A 12,000 BTU unit needs about 1,500W running plus 4,000W+ inrush — your shore service, generator, and inverter all need to handle that. We evaluate the existing electrical system during scoping and recommend upgrades if needed.

Get in touch

If you're considering a marine air conditioning install or upgrade on a sailboat, motor yacht, or catamaran in the Annapolis, Baltimore, or Washington DC area, get in touch. We'd be happy to scope the system, walk you through brand and architecture choices, and design AC that works at the dock and at anchor.