What a marine refrigerator really costs your battery bank

Start with duty cycle

A compressor fridge may draw a stated number of watts while its compressor runs, then much less while off. Multiply run power by the estimated fraction of time active and by 24 hours to estimate daily energy.

For example, 50 W at a 40% duty cycle averages 20 W and consumes about 480 Wh/day. That is an illustration; actual draw depends on temperature, insulation, ventilation, settings and use.

Heat rejection is not optional

Compressors move heat out of the cabinet. If the condenser sits in a hot, sealed locker, its runtime and electrical consumption can increase. Follow the manufacturer’s required ventilation and clearance instructions.

Adding insulation without blocking ventilation may be more useful than buying a bigger solar array.

Power budget the full trip

A weekend means repeated daily energy draws. Add lights, navigation, device charging and pumps. A modest battery that easily supports an afternoon may have less margin for multiple hot nights.

Use watt-hours for comparing across 12/24 V systems. Amp-hours only become comparable when the voltage is known.

Install for serviceability

Measure cutout and depth, opening swing, latch clearance, compressor ventilation, drain handling and electrical access. A countertop replacement might become cabinetry work if the measurements are wrong.

Some units support both DC and AC inputs; verify the actual model’s behavior and priority logic before designing around it.

Make one adjustment at a time

If energy usage is high, check gasket seal, thermostat, loading, ventilation and environment before increasing system size. Often the smartest purchase is a thermometer and a small measurement session.

Take this list shopping

• Compressor on-power recorded or researched
• Realistic duty cycle considered
• Condenser ventilation clearance verified
• Weekend energy use compared with battery usable Wh
• Dimensions and door swing checked