All guides · Diesel heating
I would choose a heating principle based on the boat’s layout and usage. Air heating sends heated air into the rooms. Hydronic (liquid-based) heating moves heat through a liquid circuit and requires heat emitters in the rooms to be heated.
Both solutions need a route through the boat
For air heating, there must be space for hot air ducts and outlets. For hydronic heating, liquid hoses must be routed to appropriate convectors, radiators, or blower units. Therefore, look at the space in cupboards, under bunks, and through bulkheads before comparing the heaters' kilowatts.
| Question | Air heating | Hydronic heating |
|---|---|---|
| How is the heat distributed? | Via ducts and outlets. | Via a liquid circuit and heat emitters. |
| What takes up space in the project? | Space for ducts, distribution, and air return paths. | Hoses, circulation, heat emitters, ventilation, and expansion. |
| Can it also produce hot water? | Possible with a suitable solution, such as combiBOIL. | Possible with a compatible tank or heat exchanger. |
| How is the price compared? | Complete air system, electricity, fuel, exhaust, and labor. | Complete liquid system and heat emitters, as well as electricity, fuel, exhaust, and labor. |
Start with three usage scenarios
Describe a cool summer evening, an autumn weekend, and the coldest trip you expect to take. Which rooms are used, for how long, and do you need hot water at the same time? This provides a better starting point than just a single temperature or the boat's length alone.
The AUTOTERM AIR series are air heaters, while the FLOW series are liquid heaters. The specific model and system setup must be suitable for the task. A liquid heater for a specific application is not automatically a complete central heating system for the boat.
Example: two different needs
A boat with a salon and a single cabin may have a straightforward need for air distribution. Another boat might already have a usable liquid circuit and several heat emitters. I would have both solutions drawn up and price out what is missing before concluding which is the simplest or cheapest.
What should be included in the total budget?
Also consider electricity consumption from pumps and fans, controls, noise considerations, and access for service. For hydronic heating, frost protection and liquid type must follow the system's requirements. For air heating, air resistance and distribution must be checked. Get a comprehensive plan where room heating and domestic hot water are evaluated separately.
Sources and manufacturer documentation
Manufacturer documentation verified 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
Tell me which rooms you want to heat, and if you also want hot water, and I will help you compare the solutions.