All guides · Cooling and water
I would choose a combiBOIL based on how the water is to be heated on your trips. The tank's capacity in liters is only one part of the choice: voltage, power, water pressure, and the interaction with the heating system must also match.
Three ways to supply heat
combiBOIL can utilize hot air, heat from a connected liquid circuit, or its electric heating element. This requires the appropriate connections and an installation intended for the chosen heat source. An electric heating element with one rated voltage cannot freely switch between 12, 24, and 230 V.
| Your use | What I would investigate |
|---|---|
| Heating in the cabin and hot water | Compatible air heater, air ducts, and water temperature control. |
| Hot water in harbor | The electric variant and the capacity in the shore power budget. |
| Existing liquid heating | Connection, temperatures, and control in the specific liquid circuit. |
7, 9, or 12 liters?
Measure both the space for the tank and access to hoses, drainage, and service. Then note whether the water will primarily be used for washing dishes, hand washing, or showers. More liters provide a larger supply, but also more water to heat and a larger tank to position.
The number of showers depends on temperature, mixing with cold water, and the flow rate of the showerhead. I would therefore use a concrete water budget rather than promising a specific number of showers per tank.
Calculation example: 7 liters on electricity
Heating 7 liters of water from 20 to 60 °C theoretically requires approximately 326 Wh. With a 300 W heating element, this corresponds to approximately 65 minutes without heat loss. In practice, heating takes longer. A 12 V/300 W heating element corresponds to 25 A at nominal values, so the battery and installation must be included in the assessment.
Check the water system before ordering
Compare the pump pressure with the manual for the specific combiBOIL chosen. Clarify pressure reduction, safety valve, expansion, and temperature limitation at the tap points. Hot water from the tank can cause scalding, and a larger pump is not automatically an improvement.
Also, make a plan for drainage and winterization. Built-in temperature control only helps when its required power, fuel, and other conditions are met. Ask for a complete component list including control and any adapters.
Sources and manufacturer documentation
Manufacturer documentation checked September 2026. Always follow the manual for the specific model and installation. The calculation examples are simplified examples for planning purposes.
Moving forward with your solution
Send information about your heater, water pump, and power supply, and I will help find a suitable combination.