i wonder if someone lived on the boat and used a lot of heat, ie not electric heaters what it would cost to heat a 30ish foot boat for a normal east coast winter ( say new york to va area ). i dont mean heating for a weekend i mean for a winter.
Here is some data from experience to help with your question: over to you
to "do the math". One gallon of diesel will run a Webasto 3500, 12,000 BTU (furnace type) heater for about 10-11 hours. This is from personal experience that also happens to match the manufacturer's claim.
That furnace is perhaps a bit larger than a 30-ft boat might need - a Webasto 2000, 7,000 BTU heater has a manufacturer's claim of 20 Hr per gallon. Based on experience with the 3500 - I have no reason to doubt the latter claim. The forced air nature of these heaters of course also requires a fan and the attendant electrical draw. There is nothing "cozy" about these things. They mount in the engine space and are designed to get as much heat from fuel as physics (and technology) will allow. No marshmallows!
In really cold Wx, I would expect a duty cycle of 75%, maybe more unless you have a well insulated boat.
s/v Auspicious - if you are out there - weigh in please. Dave has "wintered" in Annapolis harbor using (I presume) one of these.