Should I install a refrigerator or freezer on my boat, and what should I consider?

Fit a refrigerator first for everyday cruising, and add a freezer only if your provisioning plans justify the extra electricity and space it needs. Before choosing equipment, check your usable battery capacity, daily charging and box insulation: these determine how reliably refrigeration will work away from shore power.

Match capacity to your cruising

For weekends and coastal holidays, a fridge usually offers the greatest benefit: fresh food, milk and cold drinks without constant trips to buy ice. A separate freezer earns its place on longer passages, carrying frozen meals or storing food between distant provisioning stops.

Start with 40 to 80 litres for a couple's fridge and 20 to 40 litres for a modest freezer, though crew numbers and shopping habits matter more than boat length. Measure the usable interior. A large evaporator plate and awkward shelves can take up a surprising amount of space.

• Fridge only: the straightforward choice for most coastal boats.
• Fridge with a small freezing compartment: useful for ice and limited frozen supplies; check its temperature rating before relying on it for storage.
• Separate fridge and freezer: flexible provisioning, but greater installation and energy demands.
• Switchable second box: freezer for passages, additional fridge for shorter trips.

The Hallberg-Rassy 54 used that last arrangement: its second insulated box could work as a freezer or refrigerator using the same compressor. Other installations need a suitable controller and refrigeration system. Changing the thermostat alone does not guarantee conversion.

Calculate your electricity budget

Choose a marine compressor system that matches your boat's 12V or 24V supply. Common examples include equipment from Isotherm, Frigoboat and Dometic, often using Secop compressors. Check the exact unit's voltage range, low-voltage protection and installation requirements.

For planning, allow around 25 to 50Ah a day at 12V for a well-insulated 50 to 80 litre fridge in moderate weather. A small freezer can need 40 to 80Ah or more. Hot cabins, poor insulation and warm food increase consumption substantially. At 24V, the amp-hour figure is roughly half for the same energy use.

A fridge drawing 4A and running for ten hours uses 40Ah a day. That is 480Wh before other boat loads. Measure consumption over a full day with a battery monitor; compressor current alone does not tell you enough.

A nominal 100Ah lead-acid bank provides roughly 50Ah when routinely limited to 50% discharge. Refrigeration could consume most of that practical reserve before you count lights, instruments or an autopilot. Base charging capacity on actual daily output and allow for cloudy days at anchor.