@pdq: you said (and I think the ellipses are properly placed) solar water heating...may cost $80 per week to heat a large house in the Winter and only $80 per year to heat water by natural gas for that same house. Now, I'm thinking of water radiators circulating solar-heated hot water throughout the house for heat, not using solar as a means to heat water for showers, etc. Some places in my neighborhood have that set-up. Or did you mean just to provide hot water for washing?