the LP gas hot water tank is barely 2 yrs old, 40 gallon, it has a built in thermostat and I keep it dialed in about half way, temperature wise, which i prefer for my showers. the tank is super efficient, 65$ canadian in propane (100lbs) gives me at least 3 months of hot water in the summer! and turns itself off an on with the temp setting. in the winter i was previously burning 65$ in only 3 weeks using the tank plus a gas fireplace. however when I'm not using the fireplace, the LP gas lasts for several months, and the excess heat wouldn't be going out the chimney if i recirculate hot water. it would be going back into the tank. it seems to me the hot water to air heat exchanger would be far more efficient and self regulating as far as water temps, whereas the fireplace only had 3 settings, low med hi constantly burning fuel, with zero thermostat setting. i would have the air blower fan and pump only on when needed, if i need any pump at all. otherwise perhaps only a fan on a thermostat, and if a pumpless thermosyphon would work i might just add a shutoff valve for summer time. my 400 sq ft is poorly insulated , basement level, half underground, like a micro earthship, my concrete floor is about 3-4ft underground, which you might consider geothermal but in Canada the frost can go 3ft down give-or-take, just not likely when its being heated. the listed 57,000 btu is about twice what i should require, even in a Canadian poorly insulated dwelling. my geothermal floor only keeps me cool in the hot summer, it doesn't help at all in the winter, infact i use interlocking hi density floor tiles year round because of the otherwise cold floor. i would rather be overkill an be able to shut it off, or have it regulated via thermostat, rather than not have enough heat in January. last year i burned my own free dead wood but I'm not always around to keep a fire stoked. 2 yrs ago i had the LP fireplace but it was too inefficient and fuel hungry.
i love the efficiency of the LP tank and if i could use the one appliance for both the hot water and residential heat, i'd be a happy camper. i've already decided this is what i want to do this winter, and that's why i've spent money ordering parts online. i just need to figure the most efficient way to put it together with as minimal cost and maintenance as possible, for a humble frugal DIY Canadian guy like myself. its already cold here, today it tried to snow in the middle of the afternoon, and were getting frost on the pumpkins at night. i should have had this done by now, but I'm utilizing small electric plu- in heaters temporarily until the coil exchanger and pump arrive from the USA/Ebay later this week, or early next week. by then I'm hoping to know wheather or not pumpless thermosyphon is a good low maintenance possibility.