If you're using a home heating system you can collect the waste heat, flue gases, and let it pass in a heat ex changer that is submerge in the water to be heated, You can also collect the waste heat from cooking. In winter the temperature underground is higher so you might be able to pump the water back and port from tank to buried pipes. You're not going to need a big pump as the suction and delivery head is of the same level. The only energy required is overcoming the friction between the pipes and water, so using a polish pipe (inside) might help. and then of course a good insulation is a worthy investment.

I haven't tried yet or seen in real practice only a product of imagination.