[Freestyler_3]

Australia has had houses with tubes on the roof to heat the pool for a long time already.

[friend_and_foe]

I don't see the benefit here. In the summer you want a cool pool, and in the winter you need that heat to hit your house to reduce heating costs. Unless you live somewhere so warm in the winter that you still have to cool your house, in which case a pool would be pretty temperate and need no heating. If you've lived in a house like this, what's the energy benefit?

[bluGill]

In most cases the average temperature is a bit lower than what your comfortable swimming temperature is. Sure it gets hotter than that some days, but pools are very slow to heat up/cool down and so they generally track the average temperature not the peak temperature. (you are probably swimming when it is peak temperature, and not at night when it is colder outside)