This guide is intended for "seasonal boaters only". Geographical locations do effect the specifications for a heater.
For live aboard systems, you must consult an Authorized Marine Dealer.
1 meter = 3.3 feet
Click on image below for larger view.
The following guidelines will help you determine the proper heater for your boat. The heater should be sized according to the average of the guidelines below not the extremes. Keep in mind all spaces that you want heated, no matter their size. You should not expect a vent in one area to heat two spaces.
Volume – Geographic Location – Usage
The cubic area of the space(s) to be heated needs to calculated (L x W x H). This space is reduced by built in components that take away from the overall volume. How the boat is constructed determines how well it will maintain heat. The amount of windows/portholes should also be considered. The main location where the boat is used is influenced by the weather and the averages of the climate. How do you intend to use your boat? A live-aboard situation may require more heat than extending the season.
A heater that is undersized for your use may be less expensive in the beginning but will cause the unit to work overtime. This will lead to increased maintenance and premature failure of components.
A heater that is oversized for your use will cause the unit to short cycle. This will lead to increased maintenance and premature failure of components. The heater needs to operate in the high BTU range for optimum performance.