There is some misinformation in this thread about propane driers. Propane driers are quite efficient, use very little gas, and dry clothes quite quickly. First, understand clothes dry through evaporation where moisture in the fabric is transferred to the air (that's what happens when you hang them on a clothes line). The hotter the clothes are, the faster the moisture evaporates and transfers into the air (clothes hanging outside dry faster on a sunny day). In a clothes drier, the heat goes on and off intermittently to raise the temperature of the clothing for evaporation. Then it runs for a while without heat as the air flow carries the evaporating water away. Propane is much more efficient in this regard as it is a much hotter heat source than electric coils. A typical propane drier has a 17,000 to 22,000 BTU burner. There are 21,591 BTUs in a pound of propane. Typically on my propane drier at home, the burner seems to run on average less than 25% of the time (significantly more in the beginning). Consider this, If you think they aren't efficient, go look at most laundromats. It's rare to find electric heat source driers in laundromats. They want clothes to dry quickly with the lowest possible energy cost.
As to whether they make sense on a boat is another issue. I have a friend who lives in FL with his wife in a travel trailer. Their drier is in a shed hooked to a 20 lb. propane tank. Will ask him when I see them in a few days, how many loads they get to a tank of gas.
Ted