The Chofu is a very simple, and very beautiful, DIY wood-fired hot tub heater. It looks like a potbellied stove with an Eastern aesthetic, and it comes from Japan. Any container that’ll hold water can be the hot tub (metal stock tanks are a great choice). The stove is connected to the tub by two openings. The lower opening allows cold water to fill the stainless steel water jacket that makes up the Chofu’s round sides and top. As the water is heated by the fire, hot water rises to the top and pours out the upper opening into the tub, and colder water from the tank is drawn back in. This is the power of a thermo-siphon; no pump is needed. The Chofu naturally circulates the water, letting you have a hot soak completely off-grid.
We got our Chofu in the mail, and setting it up was easy; the hardest part is connecting the stovepipe parts together. It can all be done in under an hour. Stoke the fire every 45 minutes, stir the water too, and in 4 hours, a 250-gallon tank will be close to 104°F.
The Chofu setup is very open to mods: employ a lid to keep your tub cleaner, longer, without the use of chemicals, or insulate the tub to increase efficiency. It also appeals to the budget-minded.
While the stove ($863 plus shipping) and tank ($200 locally) will certainly set you back, it’s a fraction of the cost of a new manufactured hot tub, and it’ll never cost you a penny in electricity. It’s a must for the modern homestead.