I'd vote for a "solar pond heater" on the ground, near the house.
Thanks to all of you for responding to this. I found the article in
Home Power, and it says that the cost for an installed system is going
to be between $k and 5k. It is also clear you could save money by
doing it yourself, but I'm not likely to do that. I'm 60 and old enough
that I don't want to get up on a roof and sweat for several days, and I
suppose well off enouch that I can afford to have this job hired ...
share the wealth and all you know.
What I'm curious about is whether there is any great difference between
one system and another. I gather they all use the unglazed, plastic
pipe (the solar power salesman said it was made of the same material
they use to insulate electric power wires--impervious to damage from
sun, squirrels, etc. ) Is there any real difference in brand name