Discussion recently someone claimed to have used a 40 US gallon
electric hot water tank to heat a small living space by piping its
output to a couple of radiators or hydro baseboards. It was AIUI a
converted single bedroom cabin?

Presumably the hot water heater (tank) would have two 3000 watt
elements. So 6000 watts would provide approx. 18,000 BTU or so of hot
water per hour.

That sounds quite usable, recalling older less efficient hot air
circulating oil fired furnaces for 3 bedroom plus full basement houses
of 2000+ sq. feet in this rather cold climate which were often rated
at around 45,000 BTU? As long as the water would circulate somehow?

Thanks for any comments?