A fridge for your boat is one of the equipment choices with the biggest impact on power consumption while underway. Correctly chosen, a boat fridge keeps food fresh for several days without shore power; chosen incorrectly, the battery bank can drain overnight. This guide compares compressor and thermoelectric fridges, covers size selection criteria, installation location requirements, and battery sizing – so you get a working setup on the first try.
What type of fridge should you choose for a boat?
A boat fridge is a device designed to run on a boat's 12 or 24 volt DC system, withstand marine conditions, and work while tilted. There are three main types on the market: a compressor model, a thermoelectric (Peltier) model, and an absorption model.
The clear recommendation for most boaters is a compressor fridge. It's the most energy-efficient, cools effectively even in hot weather, and isn't dependent on orientation. An absorption model suits boats with a gas system and minimal electrical capacity. A thermoelectric model has the lowest purchase price, but its poor efficiency makes it a poor choice from a battery perspective.
Comparing compressor, thermoelectric, and absorption fridges
In a compressor fridge, the compressor's duty cycle in normal use is about 15–30% of total time. While running, the compressor draws 3–4 amps, but the daily average, in a well-designed installation, stays around 25–40 amp-hours. A thermoelectric model, on the other hand, draws power continuously – typically 3–5 amps around the clock.
Image name: choosing-a-fridge-for-your-boat
ALT text: A fridge suited to a boat, correctly installed with good ventilation
How do I choose the right size fridge for my boat?
A boat fridge's size is chosen based on the number of people and the number of boating days. Smaller 20–40 liter models are enough for day trips; a 50–85 liter model suits a family spending longer holidays on the boat. Fridges over 100 liters are used on larger sailboats and motorboats with a proper battery bank and shore power connection.
Recommendations by boat size and use
A practical rule of thumb: 10–12 liters per person per day. A 50-liter model is enough for a family of four on a three-day trip, when it's packed full of chilled food at departure.
How do I size the battery bank for a fridge?
Battery bank sizing is one of the most common mistakes when buying a boat fridge. A compressor model typically uses 25–45 amp-hours (Ah) over 24 hours on a 12-volt system, depending on the fridge's size, ambient temperature, and how full it is.
Example calculation: an Isotherm 49L Elegance fridge uses 265 Wh / 24h, which on a 12-volt system equals about 22 Ah. Add other equipment – lighting (10 Ah), navigation electronics (8 Ah), a pump (3 Ah) – and total consumption is about 43 Ah per day. Lead-acid batteries only use 50% of capacity, so you need at least 2 × 100 Ah = 200 Ah of battery bank to get through two days without charging. A lithium battery only needs 100 Ah for the same, since a lithium battery can be discharged to 80–90% of capacity without damage.
Read more about battery selection in our article on lithium vs. lead-acid batteries, and about total energy needs in our article on solar panel sizing for boats.
Battery sizing example by fridge size class
A solar panel is an essential part of the battery charging strategy. For a boat with a fridge, at least a 100–150W solar panel is recommended to keep the battery bank topped up on sunny summer days. If the boat has a shore power connection, that's the most convenient way to fully charge before departure. Read more: Wiring Shore Power to a Boat.
Where should a fridge be installed on a boat?
Installation location has a decisive effect on the fridge's power consumption. Poor ventilation can double consumption, since the compressor has to work harder. The three most important installation criteria are:
Ventilation: The compressor's condenser needs at least 5–10 cm of free space around it. Air must be able to circulate in and out, preferably from two different directions. A closed cabinet with no ventilation can raise the condenser's ambient temperature by 10–15°C, increasing consumption by up to 30–50%.
Protection from sun: Place the unit in as shaded a spot as possible, under the front seats or in the salon. Avoiding direct sunlight saves significant energy.
Mounting angle: A compressor fridge works even at up to a 30-degree tilt, but level installation is optimal. When buying, make sure the model is designed for marine use and withstands the motion caused by waves.
Careful installation location is the single most important factor in a boat fridge's reliability. Adequate condenser ventilation can cut power consumption by 20–40% compared with a cramped cabinet.
What should you consider when choosing a boat fridge?
Before buying, it's worth paying attention to the following:
ISO 15502 energy efficiency rating: Compare fridges based on Wh/24h consumption. The Isotherm Elegance 49L uses 265 Wh/24h, an excellent result for its size class.
Low-voltage protection: Make sure the fridge has a built-in battery charge-level cutoff (low voltage cut-off). It prevents the battery bank from being drained below 11.0–11.5 volts, which would damage lead-acid batteries.
12/24V compatibility: Quality models, such as Dometic NRX and Isotherm, automatically detect operating voltage – the same fridge works on both systems.
Removable freezer compartment: On many models, the freezer compartment is removable if fridge space matters more than freezer space. This flexibility is useful on long trips.
Bluetooth control: New models, such as the Dometic NRX series, allow temperature monitoring and adjustment from a smartphone. This helps you keep an eye on the fridge's performance energy-efficiently.
Boat fridge tips for saving power
The right usage habits can save 20–30% of a fridge's power consumption:
Pre-chill food at home before moving it to the boat. Warm food stresses the compressor more.
Open the fridge less often and quickly. Every time it's opened, cold air drops out and the compressor has to work again.
Keep the fridge full. A full unit runs more efficiently than a half-empty one, since the mass stores cold.
Raise the target temperature when departing. If there's no perishable food in the fridge, +7–8°C uses noticeably less than +3–4°C.
Use the Smart Energy Control function (available on some Isotherm models). The system automatically speeds up cooling when the engine's alternator or a solar panel is producing surplus power.
Frequently asked questions about boat fridges
How much power does a boat fridge use?
A quality compressor fridge on a 12-volt system typically uses 20–45 Ah per day. The Isotherm 49L Elegance uses 265 Wh / 24h, or about 22 Ah; the Dometic NRX 44L about 29–33 Ah. A thermoelectric model uses considerably more – up to 60–100 Ah per day, since it runs continuously at full power.
Can a regular home fridge work on a boat?
An ordinary home fridge runs on 230V AC and doesn't suit a 12V system directly. It could work through an inverter, but startup current is high and efficiency poor. For marine use it's always better to choose a compressor model specifically designed as a boat fridge, which withstands waves and moisture and works on both DC and AC systems.
What size battery is needed for a fridge?
For lead-acid batteries, size at least a 200Ah house battery bank to get two days of fridge operation without charging. With lithium batteries, a smaller capacity is enough: a 100Ah LiFePO4 battery is usually enough for a day, 150–200Ah for a few days along with other equipment. Read more: Boat Electrical System Guide.
Is a compressor fridge noisy on a boat?
Quality boat fridges – such as those with a Secop BD35 or BD Micro compressor in Isotherm models, and an LG compressor in Dometic NRX models – are very quiet. The compressor only runs 15–30% of the time, so there's little noise disturbance at night. On cheaper models, vibration can transfer to the fridge housing; place a soft foam mat under the fridge to dampen vibration.
What brands of boat fridges does Marinekauppa carry?
Marinekauppa's boat fridge range includes several well-known brands: Isotherm (with a Secop compressor, reliable performance, popular on sailboats), Dometic (NRX and CRX series, modern smart features, wide size range), and other quality manufacturers. You'll also find cooler bags and compressor cooler bags for smaller needs.
Get a boat fridge from Marinekauppa
A correctly chosen boat fridge makes multi-day overnight trips comfortable without constant worry about power. A compressor model is the clear first recommendation for its energy efficiency, reliability, and suitability for marine use. Remember to size your battery bank and charging system to match the unit – a well-planned setup also works through several cloudy days.
Check out Marinekauppa's boat fridges and find the right model. If you need help with battery or solar panel sizing, also see our own guides: Solar Panel Sizing for Boats and Boat Electrical System Guide.
Sources and further reading
Isotherm – Boat fridge manufacturer (technical documentation)
Dometic – NRX and CRX series technical data
Secop – BD35 and BD Micro compressors (manufacturer data)
ISO 15502:2005 – Refrigerator energy consumption measurement standard
Marinekauppa – Boat fridges
Marinekauppa – Cooler bags
Feature | Compressor | Thermoelectric (Peltier) | Absorption (gas/electric) | ||
Power draw 24h | 25–45 Ah (12V) | 60–120 Ah (12V) | Very high on 12V | ||
Cooling power in heat | Excellent | Degrades as temperature rises | Good | ||
Freezing capability | Yes | No | Yes | ||
Works tilted | Yes (>30°) | Yes | Limited | ||
Noise level | Quiet | Silent | Silent | ||
Purchase price | €300–1,500 | €100–300 | €500–1,500 | ||
Suitability for a boat | Excellent | Weak | Moderate | ||
Boat size / use case | Recommended volume | Typical models | |||
Day trip, 2–4 people | 20–40 liters | Cooler bag/compact model | |||
Weekend boating, 2–4 people | 40–65 liters | Isotherm 42–65 L, Dometic NRX 44 L | |||
Vacation trips, 2–4 people | 65–85 liters | Isotherm Cruise 85, Dometic NRX 85 L | |||
Long trips / large boat | 85–116 liters | Isotherm Elegance 49 L+, larger models | |||
Fridge size | 24h consumption | Lead-acid (2 days) | Lithium (2 days) | ||
40–50 liters | 20–25 Ah | 2 × 80–100 Ah | 100 Ah | ||
65–85 liters | 28–38 Ah | 2 × 100–120 Ah | 120–150 Ah | ||
85–116 liters | 35–50 Ah | 2 × 120–150 Ah | 150–200 Ah | ||
Disclaimer
This guide provides general guidance only and does not replace the product manufacturer's operating, installation, or service instructions. Marinekauppa is not responsible for actions taken based on this guide or their consequences. Always check product-specific instructions and consult a qualified professional if needed.
